In this article, we'll look at how to use MVC to consume several GET APIs in a single view. We'll go over how to create a Model to store the data, a Controller action to contact the APIs and fill the Model, and a View to display the data.

The Controller in the Model-View-Controller (MVC) architecture processes data, receives user input, and returns views. It is typical for web app developers to need several APIs to retrieve data for a single view. In this situation, we may design a Controller action that queries several APIs and then sends a ViewModel to the View, which can render the retrieved information understandable.

The following steps must be followed to use multiple GET APIs in a single MVC view.

Step 1
The initial step is to create a model to store the information collected from the APIs. AclassThe Model's properties must align with the information the APIs have returned. A new or existing class can be created to represent this Model.
public class ProjectCol
    {
        public List<master> master { get; set; }
        public List<Project> projects { get; set; }
        public List<User> users { get; set; }

    }
public class master
    {
            public int Id { get; set; }
            public string RoleName { get; set; }
    }
 public class Project
    {
        public int Id { get; set; }

        public string ProjectName { get; set; }
    }
public class User
    {
        public string UserId { get; set; }
        public string Name { get; set; }
    }
Step2
Creating a Controller action to make API calls and add data to the Model comes next. GET queries to the appropriate APIs can be sent this way using the HTTPClient or WebClient libraries.
public async Task<ActionResult> ProjectTest(ProjectCol projectallot)
 {
     string url = configuration.GetValue<string>("Projectapi:BaseApi");
     ProjectCol projectAllotment = new ProjectCol();

     List<master> _master = new List<master>();
     var baseurl = ServicesEndPonit.usermanagement.Getallrole(url);
     HttpResponseMessage Res = await httpClient.GetAsync(baseurl);
     if (Res.IsSuccessStatusCode)
     {
         var data = Res.Content.ReadAsStringAsync().Result;
         _master = JsonConvert.DeserializeObject<List<master>>(data);
     }
     List<User> user = new List<User>();
     var baseurl_ = ServicesEndPonit.usermanagement.GetUsers(url);
     HttpResponseMessage Res_ = await httpClient.GetAsync(baseurl_);
     if (Res_.IsSuccessStatusCode)
     {
         var data_ = Res_.Content.ReadAsStringAsync().Result;
         user = JsonConvert.DeserializeObject<List<User>>(data_);
     }
     List<Project> projects = new List<Project>();
     var baseurl_pro = ServicesEndPonit.ProjectManagement.GetProjects(url);
     HttpResponseMessage Res_pro = await httpClient.GetAsync(baseurl_pro);
     if (Res_pro.IsSuccessStatusCode)
     {
         var data_pro = Res_pro.Content.ReadAsStringAsync().Result;
         projects = JsonConvert.DeserializeObject<List<Project>>(data_pro);
     }
     projectAllotment.projects = projects;
     projectAllotment.users = user;
     projectAllotment.master = _master;
     return View(projectAllotment);
 }

Step 3
We can provide the Model to the view after populating it with data from the APIs. The data from each API model can then be displayed in the view using the Model attributes. The view's Razor syntax can be used to accomplish this.
<div class="row">
    <div class="col-sm-4">
        <label> User</label>
        <select class="form-select" required name="AssignedTo" id="ddlAllmember">
            <option value="hidden">Select AssginTo </option>
            @foreach (var item in Model.users)
            {
                <option value="@item.UserId">@item.Name</option>
            }

        </select>
</div>
    <div class="col-sm-4">
        <label>Job Role</label>
        <select class="form-select" required name="RoleID" id="ddlJobroleId">
            <option value="hidden">Select Job role </option>
            @foreach (var item in Model.master)
            {
                <option value="@item.Id">@item.RoleName</option>
            }
        </select>
    </div>
    <div class="col-sm-4">
        <label>Project </label>
        <select class="form-select" required name="ProjectID" id="ddlProjectName">
            <option value="hidden">Select ProjectCode </option>
            @foreach (var item in Model.projects)
            {
                <option value="@item.Id">@item.ProjectName</option>
            }
        </select>
    </div>

</div>

MVC can make consuming several GET APIs in a single view difficult. Still, it is possible by defining API models, creating a Model, using the APIs in the controller, and finally providing the Model to the view.

Follow C# Corner to learn more new and amazing things about  ASP.NET MVC or to explore more technologies. If you have any queries/suggestions on the article, please leave your questions and thoughts in the comment section below. Thanks for reading, and I hope you like it.

Authentication and Authorization are two major aspects while thinking about securing your application. Security is the main concern of modern applications because anyone can steal your data if it is not secured. So, if you are going to create an application where the data security is a primary concern, then think about Authentication and Authorization.

Authentication is the process to validate an anonymous user based on some credentials and Authorization process happens just after that and grants resources to this validated user. So, we can say, it's two-step validating process before providing the access of the resources or data.

We have many techniques to validate the users, like Windows Authentication, JWT Authentication, and Cookie Authentication etc. Today, we will learn how to implement and make ASP.NET Core MVC applications more secure using Cookie-based authentication and authorization. So, let's start the demonstration and create a fresh ASP.NET Core MVC project. You can refer to the following for the step by step process of creating an ASP.NET Core MVC application.

Be sure that while creating the project, your template should be Web Application (Model-View-Controller) and change the authentication as ‘No Authentication’.
You can download the code from here.

Here, you can choose the inbuilt Authentication functionality instead of ‘No Authentication’ and it will provide the readymade code. But we are choosing ‘No Authentication’ here because we are going to add our own Cookie-based authentication functionality in this demo and you will learn how to implement the Authentication and Authorization system from scratch.

We are choosing MVC template because we would like to see some Login and Logout functionality on UI along with Authentication and Authorization using Cookies. Now, click OK and it will take a few seconds and the project will be ready. Run it for checking if everything is working fine or not. Once everything is OK, you are ready to go.

Let’s move to the starting point of the ASP.NET Core application file which is “Startup.cs” where we configure the setting for the application like configuring the required services and configuring the middleware services etc. So, implementing the Authentication features, first, we have to add the authentication and then use it. So, let’s move to Startup.cs’s ConfigureService method and add the authentication feature using the following line of code, it will be just above services.AddMvc().
services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme).AddCookie();  

Now move to Configure in the startup.cs method and use the authentication features using the following line of code, it will be just above  routing.
app.UseAuthentication();  

Following is the whole code for adding the Authentication and using it.
    using Microsoft.AspNetCore.Authentication.Cookies;  
    using Microsoft.AspNetCore.Builder;  
    using Microsoft.AspNetCore.Hosting;  
    using Microsoft.AspNetCore.Http;  
    using Microsoft.AspNetCore.Mvc;  
    using Microsoft.Extensions.Configuration;  
    using Microsoft.Extensions.DependencyInjection;  
      
    namespace CookieDemo  
    {  
        public class Startup  
        {  
            public Startup(IConfiguration configuration)  
            {  
                Configuration = configuration;  
            }  
      
            public IConfiguration Configuration { get; }  
      
            // This method gets called by the runtime. Use this method to add services to the container.  
            public void ConfigureServices(IServiceCollection services)  
            {  
                services.Configure<CookiePolicyOptions>(options =>  
                {  
                    // This lambda determines whether user consent for non-essential cookies is needed for a given request.  
                    options.CheckConsentNeeded = context => true;  
                    options.MinimumSameSitePolicy = SameSiteMode.None;  
                });  
      
                services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme).AddCookie();  
                services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);  
            }  
      
            // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.  
            public void Configure(IApplicationBuilder app, IHostingEnvironment env)  
            {  
                if (env.IsDevelopment())  
                {  
                    app.UseDeveloperExceptionPage();  
                }  
                else  
                {  
                    app.UseExceptionHandler("/Home/Error");  
                }  
      
                app.UseStaticFiles();  
                app.UseCookiePolicy();  
                app.UseAuthentication();  
                app.UseMvc(routes =>  
                {  
                    routes.MapRoute(  
                        name: "default",  
                        template: "{controller=Home}/{action=Index}/{id?}");  
                });  
            }  
        }  
    }  

We can implement Authentication through Login feature. In most of the applications today, Authorization is decided internally based on your role. So, now we are going to create account login and logout feature, so just create one more controller as ‘AccountController.cs’ inside the controllers folder and add two action methods, one for rendering the Login View and  the other one for posting user credentials data for logging in to the system. Here is the code for AccountController where we have implemented Login functionality.
    using System;  
    using System.Collections.Generic;  
    using System.Linq;  
    using System.Security.Claims;  
    using System.Threading.Tasks;  
    using Microsoft.AspNetCore.Authentication;  
    using Microsoft.AspNetCore.Authentication.Cookies;  
    using Microsoft.AspNetCore.Mvc;  
      
    namespace CookieDemo.Controllers  
    {  
        public class AccountController : Controller  
        {  
            public IActionResult Login()  
            {  
                return View();  
            }  
      
            [HttpPost]  
            public IActionResult Login(string userName, string password)  
            {  
                if(!string.IsNullOrEmpty(userName) && string.IsNullOrEmpty(password))  
                {  
                    return RedirectToAction("Login");  
                }  
      
                //Check the user name and password  
                //Here can be implemented checking logic from the database  
      
                if(userName=="Admin" && password == "password"){  
      
                    //Create the identity for the user  
                    var identity = new ClaimsIdentity(new[] {  
                        new Claim(ClaimTypes.Name, userName)  
                    }, CookieAuthenticationDefaults.AuthenticationScheme);  
      
                    var principal = new ClaimsPrincipal(identity);  
      
                    var login = HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, principal);  
      
                    return RedirectToAction("Index", "Home");  
                }  
      
                return View();  
            }  
        }  
    }  

The first login action method is rendering the UI for login page and once you fill the data required for Login as username and password then the second action method as Login will work and send the Post request to the server.

In this method, first, we will check whether username and password should not be empty then we will validate the username and password. Here, in this demonstration, we are checking the username and password with some dummy data. You can implement database login instead of this.

After validating the user information, if everything is correct then we create Identity for that user and create the cookie information for it. Based on this principal data, we try to Sign In using a generic function called "SignInAsync" and if everything goes in the right direction then we redirect to the Home page.

Now, let's create the Login view page from where we can give the functionality to the user to enter the username and password. So, right click on the Login action method and add view without a model. It will automatically create the Account folder inside the Views under that will create “login.cshtml” file. Just open it and create a container and add a form tag along with two textboxes for entering the username and password. Apart from this, create two separate buttons as “Submit” and “Reset”. Once you fill the data and click on the submit button, it will call to Login action method defined in Account Controller using POST call. So, modify the code of “login.cshtml” as follows.
    @{  
        ViewData["Title"] = "Login";  
    }  
      
    <div class="container">  
        <div class="row">          
            <div class="col-md-3">  
                <h2><strong>Login Page </strong></h2><br />  
                <form asp-action="login" method="post">  
                    <div class="form-group">  
                        <label>User Name</label>  
                        <input type="text" class="form-control" id="userName" name="userName" placeholder="Enter user name">  
                    </div>  
                    <div class="form-group">  
                        <label>Password</label>  
                        <input type="password" class="form-control" name="password" id="password" placeholder="Password">  
                    </div>  
                    <div class="form-check">  
                        <button class="btn btn-info" type="reset">Reset</button>  
                        <button type="submit" class="btn btn-primary">Submit</button>  
                    </div>  
                </form>  
            </div>  
        </div>  
    </div>  

So far we have implemented the Cookie-based Authentication functionality in Asp.Net Core MVC project. But what about Authorization. Authorization means, providing access to the authenticated user to access a resource based on role.

So, let's first understand how we can implement the Authorization in Asp.Net Core MVC. For now, if you will try to access the HOME page without sign in, you can access it. So, let’s prevent the anonymous user from accessing the HOME page directly, if someone wants to access the HOME page then they should have to go through the Authentication process and then they will be able to access it.

So, to accomplish this, let’s open the Home Controller and put the [Authorize] attribute just above to controller. You can place it at action level but here we would like to block the whole home controller functionality and if we want to access, just go and log in. So, just do something like below.
    using CookieDemo.Models;  
    using Microsoft.AspNetCore.Authorization;  
    using Microsoft.AspNetCore.Mvc;  
    using System.Diagnostics;  
      
    namespace CookieDemo.Controllers  
    {  
      
        [Authorize]  
        public class HomeController : Controller  
        {          
            public IActionResult Index()  
            {  
                return View();  
            }  
      
            public IActionResult About()  
            {  
                ViewData["Message"] = "Your application description page.";  
      
                return View();  
            }  
      
            public IActionResult Contact()  
            {  
                ViewData["Message"] = "Your contact page.";  
      
                return View();  
            }  
      
            public IActionResult Privacy()  
            {  
                return View();  
            }  
      
            [ResponseCache(Duration = 0, Location = ResponseCacheLocation.None, NoStore = true)]  
            public IActionResult Error()  
            {  
                return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });  
            }  
        }  
    }  

Note
Be sure you have cleared all cookies which have been  created based on your previous login. If you will not do this, you will be accessing the HOME page, it is because authenticated user cookie is available in browser memory.

So, let's check how it works. Run the application and try to access the Home page. You will see here that your application automatically redirects to Login page. Now let's try to provide the user information as username = "Admin" and password =" password". Once you will pass the correct credentials and login then you will redirect to HOME page. So, let'sadd the feature that shows the logged in username along with a logout button. If you click to the log out button, your cookie value will be deleted and you will redirect to login page.

So, let's open the Account Controller and add the following logout action method.
    [HttpPost]  
    public IActionResult Logout()  
    {  
          var login = HttpContext.SignOutAsync(CookieAuthenticationDefaults.AuthenticationScheme);  
          return RedirectToAction("Login");  
    }  

And now open the Index.cshtml file from the Home folder inside the Views and modify the code as follows. Here, first of all, we are trying to show the Logged In username using @User.Identity.Name and apart from this adding a link for logout.
    @{  
        ViewData["Title"] = "Home Page";  
    }  
      
    <div class="container">  
        <div class="row">  
            <div class="col-md-12">  
                <h2><strong>Home Page </strong></h2><br /><br />  
                Hello @User.Identity.Name  
                <a asp-action="logout" asp-controller="account">  
                    Logout  
                </a>  
                <br />  
                <br />  
                <h4>Welcome to Asp.Net Core Authentication and Authorization Demo!!</h4>  
            </div>  
        </div>  
    </div>  

So far, we are able to understand how to implement Authentication in Asp.Net Core MVC and how to implement Authorization and give access to validate the users. Now, let's understand how to work with multiple roles. Here we are doing everything manually with some static value, but you can change the logic and connect to the database for validating the user. So, just modify the Login method as follows where we are providing two different kinds of roles; one is Admin role and another is User role. Based on these roles, we will provide access to some of the pages.
    [HttpPost]  
    public IActionResult Login(string userName, string password)  
    {  
        if (!string.IsNullOrEmpty(userName) && string.IsNullOrEmpty(password))  
        {  
            return RedirectToAction("Login");  
        }  
      
        //Check the user name and password  
        //Here can be implemented checking logic from the database  
        ClaimsIdentity identity = null;  
        bool isAuthenticated = false;  
      
        if (userName == "Admin" && password == "password")  
        {  
      
            //Create the identity for the user  
            identity = new ClaimsIdentity(new[] {  
                        new Claim(ClaimTypes.Name, userName),  
                        new Claim(ClaimTypes.Role, "Admin")  
                    }, CookieAuthenticationDefaults.AuthenticationScheme);  
      
            isAuthenticated = true;  
        }  
      
        if (userName == "Peter" && password == "password")  
        {  
            //Create the identity for the user  
            identity = new ClaimsIdentity(new[] {  
                        new Claim(ClaimTypes.Name, userName),  
                        new Claim(ClaimTypes.Role, "User")  
                    }, CookieAuthenticationDefaults.AuthenticationScheme);  
      
            isAuthenticated = true;  
        }  
      
        if (isAuthenticated)  
        {  
            var principal = new ClaimsPrincipal(identity);  
      
            var login = HttpContext.SignInAsync(CookieAuthenticationDefaults.AuthenticationScheme, principal);  
      
            return RedirectToAction("Index", "Home");  
        }  
        return View();  
    }  

Now let's move to HomeController and remove the [Authorize] attribute from the class level and put it in action level as follows. Here we have two different action methods which point to two different views. One is pointing to Index view and another one is pointing to the Setting page. Index page can be accessible to both type of roles, either it is Admin or User but the Setting page can be accessed only by Admin role.
    public class HomeController : Controller  
    {  
            [Authorize(Roles ="Admin, User")]  
            public IActionResult Index()  
            {  
                return View();  
            }  
      
            [Authorize(Roles ="Admin")]  
            public IActionResult Setting()  
            {  
                return View();  
      
            }  

Now modify the Index.cshtml file and add one thing as Role, just modify the code as follows.
    @{  
        ViewData["Title"] = "Setting Page";  
    }  
      
    <div class="container">  
        <div class="row">  
            <div class="col-md-12">  
                <h2><strong>Setting Page </strong></h2><br /><br />  
                Hello @User.Identity.Name !, Role @User.FindFirst(claim=>claim.Type==System.Security.Claims.ClaimTypes.Role)?.Value  
                <a asp-action="logout" asp-controller="account">  
                    Logout  
                </a>  
                <br />  
                <br />  
                <h4>Admin role user can only access this page!!</h4>  
            </div>  
        </div>  
    </div>  

Now, we have added everything and it's time to run the application. So, just press F5 and it will run your application. First, go to "Login" page and login with "User" role.

Once you will log in as a User role, definitely you will be redirected to the home page because the home page is accessible to both types  the roles.

Now, let's try to access the settings page, here you will get some Access Denied error. It is because "User" role member does not allow you to access the settings page. By default, you will get the following error as per the browser. But you can customize your error and page as well. It totally depends on you.

Now, let log out of the application for the "User" role and try to log in for Admin role. As follows, you can see, we are able to access the home page.

But let try to access the setting page for "Admin" role and yes, you will be accessed the setting page.

Lastly, let me show how you can see the cookie information. For this demo, I am using the Microsoft Edge browser, you can use any other as per your choice. But cookie information saves almost in the same place for every browser. So, just go to Network tab and then Cookie tab. Here you can see all the listed Cookies.

As you know there are various types of emulators available for viewing applications. We can use the iPhone and Windows Phone simulators for browsing the application. You can open the website on a phone that is so much more satisfying than a Desktop.

In that context, when you create the MVC 4 application you can use a Mobile template to design the application. Here, I am using Visual Studio 2013 and a MVC 5 project template to design the application. We'll use the jQuery Mobile application for displaying it in the phones and tablets.

Let's create an application on Visual Studio using MVC 5 Project template and perform some CRUD operations and add jQuery Mobile and ViewSwitcher. I am using the iPhone simulator to browse the application.

Creating CRUD Operations
Step 1: Add a model class named Cricketer and add the following code:
    public enum Grade  
    {  
        A,B,C  
    }  
    public class Cricketer  
    {  
        public int ID { get; set; }  
        public string Name { get; set; }  
        public string Team { get; set; }  
        public Grade Grade { get; set; }  
    }  
    public class CricketerDbContext : DbContext  
    {  
        public DbSet<Cricketer> Cricketers { get; set; }  
    }

In the code above, we've created an Enum property and we'll add the Enum support to the View in this article later.

Step 2: Scaffold a New Controller

Step 3: Unfortunately scaffolding does not do the Enums in the Create.cshtml and Edit.cshtml pages. You can see in the following screenshot:

Step 4: So we need to update it using the following highlighted code:
    <div class="form-group">  
        @Html.LabelFor(model => model.Grade, new { @class = "control-label col-md-2" })  
        <div class="col-md-10">  
            @Html.EnumDropDownListFor(model => model.Grade)  
            @Html.ValidationMessageFor(model => model.Grade)  
        </div>  
    </div>  

Step 4: Ok. Now it's time to run the application and perform the CRUD operations.

Adding Mobile Support
You can develop it while creating the MVC 4 application with the Mobile Template but you can add the jQuery Mobile along with the MVC 5 application. You can simply have it from the NuGet Pacakges or entering the following command in the Pacakge Manager Console:

Install-Package jQuery.Mopbile.MVC

This package will add various things such as:
    A ViewSwitcher partial view and supporting Controller
    Basic _Layout.Mobile.cshtml and supporting CSS
    Newly added BundleMobileConfig.cs

Note: You can use jQuery in any mobile framework.

Now you need to modify the Global.asax file with the following highlighted code:
    protected void Application_Start()  
    {  
        AreaRegistration.RegisterAllAreas();  
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);  
        RouteConfig.RegisterRoutes(RouteTable.Routes);  
        BundleConfig.RegisterBundles(BundleTable.Bundles);  
        BundleMobileConfig.RegisterBundles(BundleTable.Bundles);  
    }

When you run the application on the iPhone simulator as in the following:

The following screenshot will open:

Now change the table in the Index.cshml page with the following code:
    <ul data-role="listview" data-filter="true" class="my_class_list">  
    @foreach (var item in Model)  
    {  
        <li>  
            <a href="@Url.Action("Details", new {item.ID})">  
                <h3>@Html.DisplayFor(modelItem => item.Name)</h3>  
                <p>@Html.DisplayFor(modelItem => item.Team) - @Html.DisplayFor(modelItem => item.Grade) Grade</p>  
            </a>  
        </li>  
    }  
    </ul>

Now just refresh the page.

In this article, I am introducing the use of Data Annotations in MVC 5 using Microsoft Visual Studio 2013 Preview. As you know I previously deployed a MVC Application in which I used various types of techniques like Adding View, Adding Model, Login, CRUD Operations, Code Migration, Searching. These are very necessary in MVC Applications but when you develop applications, it is necessary to apply validations on that app. So, here you will learn how to validate an app in MVC 5.

In that context, validations are applied in MVC applications by the following assembly:
using System.ComponentModel.DataAnnotations;  

Here I will tell you that I am creating validation logic in my Cricketers Model. When a user creates or edits any cricketer. You can see the validation on my page in the following image:

Don't Repeat Yourself
Whenever you design an ASP.NET MVC application, Don't Repeat Yourself (DRY) is the basic assumption that you need to use. This makes your code clean, reduces the amount of code and easy to maintain because the more code you write with fewer errors the more your code functions better.

In ASP.NET MVC applications, validations are defined in the Model Class and applied all over the application. The Entity Framework Code First approach and MVC are the pillar for the validation.

So, let's begin to take advantage of Data Annotation of MVC in your application with the following criteria.

Use of Data Annotation
You need to add some logic for validation in your MVC application. For adding let's start step-by-step.

Step 1: Open Cricketers.cs from the Solution Explorer.

Step 2: Add the following assembly reference at the top of your Cricketers.cs file:
using System.ComponentModel.DataAnnotations;  

Step 3: Change your code with the following code (depends on your logic):
    using System.ComponentModel.DataAnnotations;  
    using System.Data.Entity;  
    namespace MvcCricket.Models  
    {  
        public class Cricketer  
        {  
            public int ID { get; set; }  
            [Required]  
            [StringLength(50, MinimumLength=4)]  
            public string Name { get; set; }  
            [Required]  
            [Range(1,500)]  
            public int ODI { get; set; }  
            [Required]  
            [Range(1,200)]  
            public int Test { get; set; }  
            [Required]  
            public string Grade { get; set; }  
        }  
    }  

In the code above, you can see that the Required attribute is used in each property. That means that the user needs to enter the value in it. In the Name property the StringLength attribute defines the min and max length of the Name. In the ODI and TEST property the Range attribute is defined to min and max length.

Step 4: Open a Library Package Manager Console and write the following command in it:
add-migration DataAnnotations

After pressing Enter:

Step 5: Again write the following command in the Library Package Manager Console:
update-database

What does Visual Studio do? Visual Studio opens the DataAnnotations.cs file and you will see the DbMigration class is the base class of DataAnnotations. There are two methods in it. In the Up() and Down(), you will see the updated database schema. Check it out with the following code:
    namespace MvcCricket.Migrations  
    {  
        using System;  
        using System.Data.Entity.Migrations;  
        public partial class DataAnnotations : DbMigration  
        {  
            public override void Up()  
            {  
                AlterColumn("dbo.Cricketers", "Name", c => c.String(nullable: false, maxLength: 50));  
                AlterColumn("dbo.Cricketers", "Grade", c => c.String(nullable: false));  
            }  
            public override void Down()  
            {  
                AlterColumn("dbo.Cricketers", "Grade", c => c.String());  
                AlterColumn("dbo.Cricketers", "Name", c => c.String());  
            }  
        }  
    }  

You can see in the code above that the Name and Grade property are no longer nullable. You need to enter values in it. Code First ensures that the validation rules you specify on a model class are enforced before the application saves changes in the database.

Step 6: Debug your application and open the Cricketers folder.

Click on Create New Link to create some new cricketer.

That's It. If you want to know the working process of validation process then you to notice my following paragraph.

Validation Process
    public ActionResult Create()  
    {  
        return View();  
    }  
    //  
    // POST: /Cricketers/Create  
    [HttpPost]  
    [ValidateAntiForgeryToken]  
    public ActionResult Create(Cricketer cricketer)  
    {  
        if (ModelState.IsValid)  
       {  
            db.Cricketers.Add(cricketer);  
            db.SaveChanges();  
            return RedirectToAction("Index");  
        }  
        return View(cricketer);  
    }  

In the code above when the form opens in the browser the HTTP GET method is called and in the Create action method initiates. The second method HttpPost handles the post method. This method checks that the validation errors in the form and if the object finds the errors then the Create method re-creates the form, otherwise the method saves the data in the database. In here, the form is not posted to the server, because the validation error occurs in the client-side. You can also disable your JavaScript to see the error using a breakpoint.

The following is an example of that.

In Internet Explorer

In Google Chrome

Validation Summary
You can also see the changes in your Create.cshtml file when you apply the Validation in your application. Check it out in my file:
    @using (Html.BeginForm())  
    {  
        @Html.AntiForgeryToken()  
        @Html.ValidationSummary(true)  
        <fieldset class="form-horizontal">  
            <legend>Cricketer</legend>  
            <div class="control-group">  
                @Html.LabelFor(model => model.Name, new { @class = "control-label" })  
                         <div class="controls">  
                               @Html.EditorFor(model => model.Name)  
                               @Html.ValidationMessageFor(model => model.Name, null, new { @class = "help-inline" })  
                         </div>  
                  </div>  
            <div class="control-group">  
                @Html.LabelFor(model => model.ODI, new { @class = "control-label" })  
                         <div class="controls">  
                               @Html.EditorFor(model => model.ODI)  
                               @Html.ValidationMessageFor(model => model.ODI, null, new { @class = "help-inline" })  
                         </div>  
                  </div>  
            <div class="control-group">  
                @Html.LabelFor(model => model.Test, new { @class = "control-label" })  
                         <div class="controls">  
                               @Html.EditorFor(model => model.Test)  
                               @Html.ValidationMessageFor(model => model.Test, null, new { @class = "help-inline" })  
                         </div>  
                  </div>  
            <div class="control-group">  
                @Html.LabelFor(model => model.Grade, new { @class = "control-label" })  
                <div class="controls">  
                    @Html.EditorFor(model=>model.Grade)  
                    @Html.ValidationMessageFor(model => model.Grade, null, new { @class = "help-inline" })  
                </div>  
            </div>  
            <div class="form-actions no-color">  
                <input type="submit" value="Create" class="btn" />  
            </div>  
        </fieldset>  
    }   

Summary
So far this article will help you to learn to validate your MVC Application. You can also see the procedure and working procedure of Validation in my app. So just go for it.

Using DALL-E in an ASP.NET Core application involves integrating the OpenAI API into your code. We can generate multiple images based on the given text using DALL-E generate image API endpoint. First, you must develop an OpenAI API key to authorize API use. In this article, I will explain how you can use DALL-E API in the ASP.NET Core MVC application to generate images based on the text.

Agenda for the Article,
    What is OpenAI?
    What is DALL-E?
    How to get OpenAI API Key
    Generating Image In ASP.NET Core MVC

What is OpenAI?
OpenAI is an artificial intelligence research lab that works to develop and grow AI in different fields like medicine, education, sports, information technology, etc. It was founded in 2015. OpenAI conducts research in various areas of AI, including machine learning, natural language processing, robotics, and computer vision. The organization has developed several groundbreaking AI models, including GPT-3, DALL-E, and CLIP. In this article, I will explain the use of the DALL-E. I have also written an article on GPT-3. To know more, please refer to this article.

What is DALL-E?
DALL-E is an artificial intelligence (AI) program developed by OpenAI that generates images from textual descriptions using a transformer-based language model. DALL-E is named after the famous artist Salvador Dali. The program can create highly detailed and complex images of objects, animals, and scenes that do not exist in the real world but also in the real world. It works by learning from a dataset of images and their associated textual descriptions, allowing it to generate fictional and realistic images based on the given textual input. DALL-E is a significant breakthrough in AI image generation and has the potential to revolutionize various industries, including advertising, gaming, and e-commerce.

Generating OpenAI API Key
You need to authorize the API endpoint by passing the API key. To generate an OpenAI API key, follow these steps:

Signup for an OpenAI account. Go to the OpenAI website and create a new account.
Confirm your email address.
Now, Log in to your account and navigate to the 'View API keys' section as given below.

Now, click on 'Create new secret key' as given below.

Store your API key in a secure location, as it will be required to access the OpenAI APIs. You can copy the key and save it for future use. OpenAI has usage and resource limitations for its API, so be sure to check its documentation here for details on usage and pricing.

Generating Image In ASP.NET Core MVC
To generate images in the ASP.NET Core MVC application using DALL-E, you need to follow the below-given steps:
    First, create an ASP.NET Core MVC project. To know more about creating a project, please refer here.
    Add your API key in the appsettings.json file as given below

    //demo key
    "OpenAI_API_KEY": "sk-cF8Dv3n2YtUXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"

Add the below-given code for the UI in your Index.cshtml file inside Views>Home>Index.cshtml
<h1 class="display-4">Image Generator</h1>
<!--Image info-->
<input type="text" class="form-control" id="txt" style="width:400px;" placeholder="Image Description" />
<br />
<!--Image Size-->
<select id="size">
    <option selected>256x256</option>
    <option>512x512</option>
</select>
<!--Images Required-->
<input type="number" value="1" placeholder="Images Required" id="quantity" />
<!--Generate button-->
<button id="generate">
    Generate
</button>
<br />
<!--Display image here-->
<div id="Imagedisplay" class="col-md-14 row">
</div>

In the above-given code, you have added a UI for the home page to enter some basic details required for the image, like the information about the image, the number of images required, and the size of the image.

Now you will add a model class ImageInfo.cs inside the Models folder as given below.
public class ImageInfo {
    public string ? ImageText {
        get;
        set;
    }
}
public class RequiredImage {
    public string ? prompt {
        get;
        set;
    }
    public short ? n {
        get;
        set;
    }
    public string ? size {
        get;
        set;
    }
}
public class ImageUrls {
    public string ? url {
        get;
        set;
    }
}
// response handling
public class ResponseModel {
    public long created {
        get;
        set;
    }
    public List < ImageUrls > ? data {
        get;
        set;
    }
}

In the above-given code, You have added ResponseModel class for handling the response and RequiredImage class for the input data about the required image.

Now you will add a controller method inside HomeController.cs as given below.
[HttpPost]
public async Task < IActionResult > GenerateImage([FromBody] RequiredImage obj) {
    string imglink = string.Empty;
    var response = new ResponseModel();
    using(var client = new HttpClient()) {
        client.DefaultRequestHeaders.Clear();
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", APIKEY);
        var Message = await client.PostAsync("https://api.openai.com/v1/images/generations", new StringContent(JsonConvert.SerializeObject(obj), Encoding.UTF8, "application/json"));
        if (Message.IsSuccessStatusCode) {
            var content = await Message.Content.ReadAsStringAsync();
            response = JsonConvert.DeserializeObject < ResponseModel > (content);
            imglink = resp.data[0].url.ToString();
        }
    }
    return Json(response);
}

You have added a post-call with the DALL-E API key in the above given code. You have to pass the API key shown above.

The final step is to display the image on the UI using javascript. So you have to add the below-given code inside wwwroot>js>site.js.
$(document).ready(() => {
    $('#generate').click(function() {
        var info = {};
        info.n = parseInt($('#quantity').val());
        info.prompt = $('#txt').val();
        info.size = $('#size').find(":selected").val();
        $.ajax({
            url: '/Home/GenerateImage',
            method: 'post',
            contentType: 'application/json',
            data: JSON.stringify(info)
        }).done(function(data) {
            $.each(data.data, function() {
                $('#Imagedisplay').append('<div class="col-md-5" style="padding-top:12px">' + '<img class="p-12" src = "' + this.url + '"/>' + '</div>');
            });
        });
    });
});

Output

Conclusion
OpenAI provides us with lots and lots of use for artificial intelligence. AI has become a part of our daily life nowadays. ChatGPT and DALL-E are all advanced and great examples of AI. To generate an image, you need two things. First, the OpenAI APOI key and second DALL-E API endpoint. Pass the API key in the header and freely use that endpoint.

Thank You, and Stay Tuned for More.

Why Design Pattern?
Traditionally, what do we do? We access our database directly, without using any middle layer or Data Access Layer (DAL).

Do you think this is a good approach? No, it's not! Here is why.
 
The tight coupling of the database logic in the business logic makes applications complex, tough to test, and tough to extend further. Direct access to the data in the business logic causes many problems like difficulty in completing the Unit Test of the business logic, disability to test business logic without the dependencies of external systems like a database, and a duplicate data access code throughout the business layer. I hope we now know why we need a design pattern. There are many types of design patterns but in today’s article, we will discuss repository design pattern.
 
What is a Repository Design Pattern?
By definition, the Repository Design Pattern in C# mediates between the domain and the data mapping layers using a collection-like interface for accessing the domain objects. Repository Design Pattern separates the data access logic and maps it to the entities in the business logic. It works with the domain entities and performs data access logic. In the Repository pattern, the domain entities, the data access logic, and the business logic talk to each other using interfaces. It hides the details of data access from the business logic.
 
Advantages of Repository Design Pattern

• Testing controllers becomes easy because the testing framework need not run against the actual database access code.
• Repository Design Pattern separates the actual database, queries and other data access logic from the rest of the application.
• Business logic can access the data object without having knowledge of the underlying data access architecture.
• Business logic is not aware of whether the application is using LINQ to SQL or ADO.NET. In the future, underlying data sources or architecture can be changed without affecting the business logic.
• Caching strategy for the data source can be centralized.
• Centralizing the data access logic, so code maintainability is easier

Non-Generics Repository Design Pattern Source Code
Generics Repository Design Pattern Source Code

Implementation
Let’s do it practically and see how it implements. We will take a very basic example of implementation. I have attached the code file that you can download from the above link. I try to do it step by step and explained each step so that you can understand better. I full try to make it simple, clear and understandable.
 
Step 1
Let’s create a simple database (BasicDb) containing a single table with the name of Product_Table. The Backup and Script file is attached simply download it and restore it in SQL. You can choose any one file for restoration.
 
Step 2
Create the Asp.Net MVC Project with the name of (Repository Design Pattern) screenshots are below.

Select MVC

Step 3
Create an Entity Framework to give the model name DataContext.

Select Entity framework designer from the database.

Select Database

Change name to (DataContext) it is optional you can keep as it is,

Select Table

Step 4
Create a Folder in the model folder with the name (DAL) where we will implement our repository.

Step 5
Create an Interface Class (IProductRepository.cs)

Paste this Code to IProductRepository.cs,
    using System;  
    using System.Collections.Generic;  
    using System.Linq;  
    using System.Text;  
    using System.Threading.Tasks;  
      
    namespace Repositiory_Pattern.Models.DAL  
    {  
        interface IProductRepository  
        {  
            IEnumerable<Product_Table> GetProducts();  
            Product_Table GetProductById(int ProductId);  
            void InsertProduct(Product_Table product_);  
            void UpdateProduct(Product_Table product_);  
            void DeleteProduct(int ProductId);  
            void SaveChanges();  
        }  
    }

IProductRepository.cs

Step 6
Create a class in the DAL folder (ProductRepository.cs) This will be child class and will implement all the methods of (IProductRepository.cs) class. Paste this Code
    using System;  
    using System.Collections.Generic;  
    using System.Linq;  
    using System.Web;  
      
    namespace Repositiory_Pattern.Models.DAL  
    {  
        public class ProductRepository:IProductRepository  
        {  
            private DataContext _dataContext;  
            public ProductRepository(DataContext dataContext)  
            {  
                this._dataContext = dataContext;  
            }  
            public void DeleteProduct(int ProductId)  
            {  
                Product_Table product_ = _dataContext.Product_Table.Find(ProductId);  
                _dataContext.Product_Table.Remove(product_);  
            }  
            public Product_Table GetProductById(int ProductId)  
            {  
                return _dataContext.Product_Table.Find(ProductId);  
            }  
            public IEnumerable<Product_Table> GetProducts()  
            {  
                return _dataContext.Product_Table.ToList();  
            }  
            public void InsertProduct(Product_Table product_)  
            {  
                _dataContext.Product_Table.Add(product_);  
            }  
            public void SaveChanges()  
            {  
                _dataContext.SaveChanges();  
            }  
            public void UpdateProduct(Product_Table product_)  
            {  
             _dataContext.Entry(product_).State = System.Data.Entity.EntityState.Modified;  
            }  
        }  
    }

ProductRepository.cs

Step 7
Now just go to our built-in Home Controller and paste this code.
    using Repositiory_Pattern.Models;  
    using Repositiory_Pattern.Models.DAL;  
    using System;  
    using System.Collections.Generic;  
    using System.Linq;  
    using System.Web;  
    using System.Web.Mvc;  
      
    namespace Repositiory_Pattern.Controllers  
    {  
        public class HomeController : Controller  
        {  
            private IProductRepository _productRepository;  
            public HomeController()  
            {  
                this._productRepository = new ProductRepository(new DataContext());  
            }  
            public ActionResult Index()  
            {  
                return View(_productRepository.GetProducts());  
            }       
            public ActionResult Create()  
            {  
                return View(new Product_Table());  
            }  
            [HttpPost]  
            public ActionResult Create(Product_Table product)  
            {  
                _productRepository.InsertProduct(product);  
                _productRepository.SaveChanges();  
                return RedirectToAction("Index");  
            }              
            public ActionResult Update(int Id)  
            {  
                return View(_productRepository.GetProductById(Id));  
            }  
            [HttpPost]  
            public ActionResult Update(Product_Table product)  
            {  
                _productRepository.UpdateProduct(product);  
                _productRepository.SaveChanges();  
                return RedirectToAction("Index");  
            }              
            public ActionResult Delete(int Id)  
            {  
                _productRepository.DeleteProduct(Id);  
                _productRepository.SaveChanges();  
                return RedirectToAction("Index");  
            }  
        }  
    }

HomeController.cs

Step 8
Now create the views Index, Create and Update. Just right click on the method name.
 
Index.cshtml

Create.cshtml

Update.cshtml

Step 9
Open the Index view and change the action name Edit to Update and save.

Step 10
Now just run and see the result in the browser.

In this project, we have performed CRUD operations using the Repository design pattern. We have created a single interface (IProductRepository.cs) and implemented all their methods in (ProductRepository.cs). Now if we have multiple entities or models then will we make an interface for each entity? No
 
We will not do this whereas we will make a single Generic (IModelRepository.cs) and (ModelRepository.cs) if we have multiple models we will use only a single interface and their single implementation class. The Generic Repository Project code I have attached so you can download it from the above mention link. If you have any queries about the problem you face please comment below I will answer.

Overview on ASP.NET

Let’s differentiate both.

.NET Framework

• Developed and run on Windows platform only.
• Built on the .NET Framework runtime.
• Supported (MVC, Web API & SignalR) Dependency Injection (DI).
• MVC & Web API Controller are separated.

.Net Core

• Open Source.
• Developed & run on Cross Platform.
• Built on the .NET Core runtime & also on .NET Framework.
• Facility of dynamic compilation.
• Built in Dependency Injection (DI).
• MVC & Web API Controller are unified, Inherited from same base class.
• Smart tooling (Bower, NPM, Grunt & Gulp).
• Command-line tools.

Start with .NET Core 1.0
Let’s create a new project with Visual Studio 2015 > File > New > Project.

Choose empty template and click OK.

Visual Studio will create a new project of ASP.NET Core empty project.

We will now explore all initial files one by one.

Explore Initial Template

Those marked from Solution Explorer are going to be explored, one by one.

First of all, we know about program.cs file. Let’s concentrate on it.

Program.cs: Here, we have sample piece of code. Let’s get explanation.
    namespace CoreMVCAngular  
    {  
        public class Program   
        {  
            public static void Main(string[] args) {  
                var host = new WebHostBuilder().UseKestrel().UseContentRoot(Directory.GetCurrentDirectory()).UseIISIntegration().UseStartup < Startup > ().Build();  
                host.Run();  
            }  
        }  
    }  

.UseKestrel() : Define the Web Server. ASP.NET Core supports hosting in IIS and IIS Express.

HTTP servers
    Microsoft.AspNetCore.Server.Kestrel (cross-platform)
    Microsoft.AspNetCore.Server.WebListener (Windows-only)

.UseContentRoot(Directory.GetCurrentDirectory()) : Application base path that specifies the path to the root directory of the Application.
.UseIISIntegration() : For hosting in IIS and IIS Express.
.UseStartup<Startup>() : Specifies the Startup class.
.Build() : Build the IWebHost, which will host the app & manage incoming HTTP requests.

Startup.cs
This is the entry point of every .NET Core Application. It provides services, that the Application required.
    namespace CoreMVCAngular   
    {  
        public class Startup   
        {  
            // This method gets called by the runtime. Use this method to add services to the container.  
            // For more information on how to configure your application, visit http://go.microsoft.com/fwlink/?LinkID=398940  
            public void ConfigureServices(IServiceCollection services) {}  
                // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.  
            public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory) {}  
        }  
    }  

As you can see, there are two methods; one is ConfigureServices & another is Configure. In Configure method, three parameters are specified.

IApplicationBuilder defines a class, which provides the mechanisms to configure an Application's request.

We can add MVC (middleware) to the request pipeline by using “Use” extension method. Later, we will use it.
ConfigureServices is an extension method, which is configured to use the several services.

Project.json: This is where our Application dependencies are listed i.e by name & version. This file also manages runtime, compilation settings.

Dependencies: All Application dependencies can add new dependencies, if required, intellisense will help up to include with the name & version.

After saving changes, it will automatically restore the dependencies from NuGet.

Here, the code snippet is changed.
    "dependencies": {  
    "Microsoft.NETCore.App": {  
    "version": "1.0.0",  
    "type": "platform"  
    },  
    "Microsoft.AspNetCore.Diagnostics": "1.0.0",  
      
    "Microsoft.AspNetCore.Server.IISIntegration": "1.0.0",  
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.0",  
    "Microsoft.Extensions.Logging.Console": "1.0.0",  
    "Microsoft.AspNetCore.Mvc": "1.0.0"  
    },  

To uninstall, go to Solution explorer > right click on package > Uninstall package.

Tools: This section manages and lists command line tools. We can see IISIntegration.Tools is added by default, which is a tool that contains dotnet publish iis command for publishing the Application on IIS.
    "tools": {  
    "Microsoft.AspNetCore.Server.IISIntegration.Tools": "1.0.0-preview2-final"  
    },  

Frameworks: As we can see, initially our app is running on the .NET Core platform by default with the runtime.
    “netcoreapp1 .0”.  
    "frameworks": {  
        "netcoreapp1.0": {  
            "imports": ["dotnet5.6", "portable-net45+win8"]  
        }  
    },  

Build Options: Options, which are passed to the compiler while building the Application.
    "buildOptions": {  
        "emitEntryPoint": true,  
        "preserveCompilationContext": true  
    },  

RuntimeOptions: Manage Server garbage collection at Application runtime.
    "runtimeOptions": {  
        "configProperties": {  
            "System.GC.Server": true  
        }  
    },  

PublishOptions: This defines the file/folder to include/exclude to/from the output folder, while publishing the Application.
    "publishOptions": {  
        "include": ["wwwroot", "web.config"]  
    },  

Scripts: Scripts is an object type, which specifies that scripts run during building or publishing the Application.
    "scripts": {  
        "postpublish": ["dotnet publish-iis --publish-folder %publish:OutputPath% --framework %publish:FullTargetFramework%"]  
    }  

Add MVC6
It’s time to add MVC6. In .NET Core 1.0 MVC & Web API are unified, and become a single class, which inherits from the same base class.

Let’s add MVC Service to our Application. Open project.json to add new dependencies in it. In dependencies section, add two dependencies.
    "Microsoft.AspNetCore.Mvc": "1.0.0",
    "Microsoft.AspNetCore.StaticFiles": "1.0.0"

Click Save.

It will start restoring the packages automatically.

Now let’s add MVC (midleware) to request pipeline in Config method at startup class.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory) {  
        loggerFactory.AddConsole();  
        if (env.IsDevelopment()) {  
            app.UseDeveloperExceptionPage();  
        }  
        //app.UseStaticFiles();  
        app.UseMvc(routes => {  
            routes.MapRoute(name: "default", template: "{controller=Home}/{action=Index}/{id?}");  
        });  
    }  

In ConfigureServices method, we need to add framework Service. We have added services.AddMvc();
    public void ConfigureServices(IServiceCollection services) {  
        services.AddMvc();  
    }  

MVC Folder Structure

Let’s add MVC folder structure to our sample Application. We have added view files in the views folder & MVC controller in Controllers folder like old MVC Application.

Here, you may notice that there is a new file in the views folder “_ViewImports.cshtml”. This file is responsible for setting up the namespaces, which can be accessed by the views in the project, which was previously done by the Web.config file in the views folder.

We are almost done. Let’s modify our view content with welcome message. Now, run the Application. You can see welcome message appears in the home page.

Output

AngularJS2
AngularJS2 is a modern Client end JavaScript Framework for the Application development. This JavaScript framework is totally new & written, based on TypeScript.

We will follow the steps, given below, to learn, how we install it to our Application,
    Manage Client-side Dependencies
    Use Package Manager (NPM).
    Use Task Runner.
    Bootstrapping using Type Script.

Client-side Dependencies: We need to add a JSON config file for Node Package Manager(NPM). Click add > New Item > Client- Side > npm Configuration File and click OK.

Open our newly added npm config file and modify the initial settings.

Package.json
    {  
        "version": "1.0.0",  
        "name": "asp.net",  
        "private": true,  
        "Dependencies": {  
            "angular2": "2.0.0-beta.9",  
            "systemjs": "0.19.24",  
            "es6-shim": "^0.33.3",  
            "rxjs": "5.0.0-beta.2"  
        },  
        "devDependencies": {  
            "gulp": "3.8.11",  
            "gulp-concat": "2.5.2",  
            "gulp-cssmin": "0.1.7",  
            "gulp-uglify": "1.2.0",  
            "rimraf": "2.2.8"  
        }  
    }  

In the dependencies section, we need to add AngularJS2 with other dependencies and they are for:
    Es6-shim is a library, which provides compatibility on old environment.
    Rxjs provides more modular file structure in a variety of formats.
    SystemJS enables System.import TypeScript files directly.

As you can see, there are two different type objects; one is dependencies, which are used for the production purposes & the other one is devDependencies for development related things, like gulp is to run different tasks.

Click save. It will restore automatically. Here, we have all our required packages in the Dependencies section.

In this application we have added another package manager called Bower, Click add > New Item > Client- Side > Bower Configuration File then click Ok.

Comparing with NPM,
Bower:
    Manage html, css, js component
    Load minimal resources
    Load with flat dependencies

NPM:
    Install dependencies recursively
    Load nested dependencies
    Manage NodeJS module

Open the config file then add required dependencies in dependencies secction with specific version.

Save the JSON file after edit, it will automatically restore that package in our project. Here you can see we have added Jquery & Bootstrap package with Bower package manager.

Now, let’s add a gulp configuration file to run the task. Click Add > New Item > Client-Side. Select gulp JSON file to include.

Gulp.json
    /*
    This file in the main entry point for defining Gulp tasks and using Gulp plugins.
    Click here to learn more. http://go.microsoft.com/fwlink/?LinkId=518007
    */  
    "use strict";  
    var gulp = require("gulp");  
    var root_path = {  
        webroot: "./wwwroot/"  
    };  
    //library source  
    root_path.nmSrc = "./node_modules/";  
    //library destination  
    root_path.package_lib = root_path.webroot + "lib-npm/";  
    gulp.task("copy-systemjs", function() {  
        return gulp.src(root_path.nmSrc + '/systemjs/dist/**/*.*', {  
            base: root_path.nmSrc + '/systemjs/dist/'  
        }).pipe(gulp.dest(root_path.package_lib + '/systemjs/'));  
    });  
    gulp.task("copy-angular2", function() {  
        return gulp.src(root_path.nmSrc + '/angular2/bundles/**/*.js', {  
            base: root_path.nmSrc + '/angular2/bundles/'  
        }).pipe(gulp.dest(root_path.package_lib + '/angular2/'));  
    });  
    gulp.task("copy-es6-shim", function() {  
        return gulp.src(root_path.nmSrc + '/es6-shim/es6-sh*', {  
            base: root_path.nmSrc + '/es6-shim/'  
        }).pipe(gulp.dest(root_path.package_lib + '/es6-shim/'));  
    });  
    gulp.task("copy-rxjs", function() {  
        return gulp.src(root_path.nmSrc + '/rxjs/bundles/*.*', {  
            base: root_path.nmSrc + '/rxjs/bundles/'  
        }).pipe(gulp.dest(root_path.package_lib + '/rxjs/'));  
    });  
    gulp.task("copy-all", ["copy-rxjs", 'copy-angular2', 'copy-systemjs', 'copy-es6-shim']);  

To run the task, right click on Gulp.json file to reload.

Right click on copy-all & click run.

Task run & finish.

In Solution Explorer, all the required packages are copied. We also need to put the type definitions for es6-shim(typing folder), without this, it will cause error - "Cannot find name 'Promise'".

Bootstrapping with TypeScript

tsConfig.json
    {  
        "compilerOptions": {  
            "noImplicitAny": false,  
            "noEmitOnError": true,  
            "removeComments": false,  
            "sourceMap": true,  
            "target": "es5",  
            //add this to compile app component  
            "emitDecoratorMetadata": true,  
            "experimentalDecorators": true,  
            "module": "system",  
            "moduleResolution": "node"  
        },  
        "exclude": ["node_modules", "wwwroot/lib"]  
    }  

noImplicitAny : Raise an error on the expressions and declarations with an implied ‘any’ type.
noEmitOnError : Do not emit outputs, if any errors were reported.
Target : Specify ECMAScript target version: ‘es5’ (default), ‘es5’, or ‘es6’.
experimentalDecorators : Enables an experimental support for ES7 decorators.

Create an app folder for .ts file in wwwroot folder.

In Solution Explorer, you may add the files, given below.

In main.ts code snippet, bootstrap AngularJS with importing the component.

    import {bootstrap} from 'angular2/platform/browser';  
    import {AppComponent} from './app.component';  
    import {enableProdMode} from 'angular2/core';  
      
    enableProdMode();  
    bootstrap(AppComponent);  

Component: imports the Component function from Angular 2 library; use of import, app component class can be imported from other component.
import {Component} from 'angular2/core';

    @Component({  
        selector: 'core-app',  
        template: '<h3>Welcome to .NET Core 1.0 + MVC6 + Angular 2</h3>'  
    })  
    export class AppComponent {}  

MVC View: It’s time to update our layout & linkup the library.

Now, we will add the reference to our layout page.
    <!DOCTYPE html>  
    <html>  
      
    <head>  
        <meta name="viewport" content="width=device-width" />  
        <title>@ViewBag.Title</title>  
        <script src="~/lib-npm/es6-shim/es6-shim.js"></script>  
        <script src="~/lib-npm/angular2/angular2-polyfills.js"></script>  
        <script src="~/lib-npm/systemjs/system.src.js"></script>  
        <script src="~/lib-npm/rxjs/Rx.js"></script>  
        <script src="~/lib-npm/angular2/angular2.js"></script>  
    </head>  
      
    <body>  
        <div> @RenderBody() </div> @RenderSection("scripts", required: false) </body>  
      
    </html> Index.cshtml @{ ViewData["Title"] = "Home Page"; }  
    <core-app>  
        <div>  
            <p><img src="~/img/ajax_small.gif" /> Please wait ...</p>  
        </div>  
    </core-app> @section Scripts {  
    <script>  
        System.config({  
            packages: {  
                'app': {  
                    defaultExtension: 'js'  
                }  
            },  
        });  
        System.import('app/main').then(null, console.error.bind(console));  
    </script> }  

One more thing to do is to enable the static file serving. Add this line to startup config method.
app.UseStaticFiles();

Build & run application

Finally, build & run the Application.

Here, we can see our app is working with AngularJS2.

There are two influential books released by Steve Souders on Web Performance named High Performance Web Sites and Even Faster Web Sites. The conclusion of these books changed the face of the web development and have been codified into several performance analysis tools including Yahoo YSlow and Google PageSpeed.

In the web application development, most web developers follow the recommendations written by the Steve Souders to be implemented. Some are the following:

    You can enable the HTTP Caching and Content Compression easily via a few settings in the Web.Config file.
    Layout pages make it easy to put stylesheets at the top of the page and information about the scripts present at the bottom of the page in a very consistent manner.
    You can get the ability to blend and reduce the assets by the Microsoft.AspNet.Web.Optimization NuGet Package.

Overview
I am describing Flushing in the MVC. So, what is this Flushing? Let's simplify this: Flushing is when the server sends the initial part of the HTML doc to the client before the entire response is ready. Then all main browsers parse the partial response. When it is done successfully, flushing results in a page that loads and feels faster. The key is choosing the right point at which to flush the partial HTML document response. A flush should be done before database queries and web service calls.

What is the Conflict?
In the .NET Framework 1.1, you can use the mechanism to flush a response stream to the client with a simple call to the HttpResponse.Flush(). This works very fine when you start to build the response. The MVC architecture doesn't really allow this command pattern. You can use it in MVC as in the following:
    @{ 
        Response.Flush(); 
    }

You can do this because at first MVC executes the controller before the View execution.

Getting Started
Instal the Optimization package in MVC using the following command in the Package Manager Console:
Install-Package Microsoft.AspNet.Web.Optimization

We can get it by manually executing and flushing the partial results:
    public ActionResult FlushSample() 
    { 
        PartialView("About").ExecuteResult(ControllerContext); 
        Response.Flush(); 
        return PartialView("Basic"); 
    }

If we want to use it in the controller then we can create it as in the following:
    public class ViewController : Controller 
    { 
        public void FlushSample(ActionResult action) 
        { 
            action.ExecuteResult(ControllerContext); 
            Response.Flush(); 
        } 
    }

The FlushSample() method clarifies the intent in the action method. And after in the same class:
    public ActionResult DemoFlush() 
    { 
        FlushSample(PartialView("About"); 
        return PartialView("Basic"); 
    }

We can also use the yield keyword and split the layout file into multiple partial views, as shown in the code below:
    public IEnumerable<ActionResult> DemoFlush() 
    { 
        yield return PartialView("Index"); 
        Thread.Sleep(5000); 
        yield return PartialView("About"); 
        Thread.Sleep(2000); 
        yield return PartialView("Basic"); 
    }

This article described the use of flushing in the MVC. In the future flushing can be used more effectively. Thanks for reading and Stay Updated.

In this tutorial, I am going to explain how to display an image from a byte array in ASP.NET MVC using C# .NET and VB.NET.

• Open Visual Studio and create a new MVC project.
• Once the project is loaded, right-click on the Controllers folder and add a new Controller.
• Create an Images folder in your project and add a sample image.
• Now, open the DemoController and add the GetImageFromByteArray action method.
• Within the action method, place the code given below (Below, I have given the entire Controller code).

  

C#.NET Code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace DemoProject.Controllers
{
    public class DemoController : Controller
    {
        // GET: Demo/GetImageFromByteArray
        public ActionResult GetImageFromByteArray()
        {
            // Get image path
            string imgPath = Server.MapPath("~/images/self-discipline.png");
            // Convert image to byte array
            byte[] byteData = System.IO.File.ReadAllBytes(imgPath);
            //Convert byte arry to base64string
            string imreBase64Data = Convert.ToBase64String(byteData);
            string imgDataURL = string.Format("data:image/png;base64,{0}", imreBase64Data);
            //Passing image data in viewbag to view
            ViewBag.ImageData = imgDataURL;
            return View();
        }
    }
}

VB.NET Code
    Imports System.Collections.Generic
    Imports System.Linq
    Imports System.Web
    Imports System.Web.Mvc

    Namespace DemoProject.Controllers
        Public Class DemoController
            Inherits Controller
            ' GET: Demo/Image
            Public Function GetImageFromByteArray() As ActionResult
                ' Get image path
                Dim imgPath As String = Server.MapPath("~/images/self-discipline.png")
                ' Convert image to byte array
                Dim byteData As Byte() = System.IO.File.ReadAllBytes(imgPath)
                'Convert byte arry to base64string
                Dim imreBase64Data As String = Convert.ToBase64String(byteData)
                Dim imgDataURL As String = String.Format("data:image/png;base64,{0}", imreBase64Data)
                'Passing image data in viewbag to view
                ViewBag.ImageData = imgDataURL
                Return View()
            End Function
        End Class
    End Namespace

Now, let me explain what is there in the code.

• I read the image from the folder into an imgPath local variable.
• In the second step, I converted the image into a byte array using the ReadAllBytes method.
• And then, I converted the byte array into base 64 string format using Convert.ToBase64String method.
• Now, I have appended data:image/png;base64 at the beginning of the base64 string so that the browser knows that the src attribute value itself contains the image data.
• Finally, I have assigned this image data in the ViewBag and returned it to the View.

Now, add a new View to the GetImageFromByteArray action method. And add an image view. We can directly assign the image data from ViewBag to src attribute of the image tag like below.
@{
    ViewBag.Title = "Asp.Net MVC Display image from byte array";
}

<h2>Asp.Net MVC Display image from byte array</h2>
<img src="@ViewBag.ImageData">

Output
Now, if you run the program, you can see the output of how to display the image from the byte array.

Now, if you look into the source of the page, you can see the base 64 string rendered as an image.

I hope you learned how to display the image from a byte array in ASP.NET. Please post your comments and feedback below.

As you know, we can perform CRUD operations in MVC 5 with an Entity Framework Model and we also work in Paging & Searching in MVC 5. Now, suppose we want to update the database with new details in the Students, Courses and Enrollments entities, then we need to migrate our application.

In that context, you'll learn today to do the Code First Migration in the MVC application. The migration helps you to update and change the data model that you've created for the application and you don't need to re-create or drop your database. So, let's proceed with the following section.

Apply Code First Migration
The data model in the database usually changes after developing the new application. When the data model changes, it becomes out of sync with the database. We've configured our Entity Framework in the app to drop and recreate the data model automatically. When any type of change is done in the entity classes or in the DbContext class, the existing database is deleted and the new database is created that matches the model and sees it with test data.

When the application runs in production, we do not want to loose everything each time we make changes like adding a column. The Code First Migration solved this problem by enabling the code first to update the database instead of dropping or recreating.

Use the following procedure to create a sample of that.

Step 1: Please disable the Database Initializer in the Web.Config file or in the Global.asax file like as in the following:
In Web.Config File:
    <!--<contexts> 
          <context type="Vag_Infotech.DAL.CollegeDbContext, Vag_Infotech"> 
            <databaseInitializer type="Vag_Infotech.DAL.CollegeDatabaseInitializer, Vag_Infotech"></databaseInitializer> 
          </context> 
    </contexts>--> 

In Global.asax File:

    // Database.SetInitializer(new CollegeDatabaseInitializer());

Step 2: Please change the database name in the Web.Config file like as in the following:
    <connectionStrings>  
      <add name="CollegeDbContext" connectionString="Data Source=(LocalDb)\v11.0;Initial Catalog=VInfotechNew;Integrated Security=SSPI" providerName="System.Data.SqlClient" /> 
    </connectionStrings> 

Step 3: Open the Package Manager Console and enter the following commands:
enable-migration

add-migration InitialCreate

It'll create the Migration folder in your application and Configuration.cs file in it automatically.

You can see the Seed() created in the file and the purpose of this method is to enable the insert or change data after Code First creates or updates the database.

Editing Seed Method
Now, we add new code for updating our data model in this method. When we do not use the migration, the data model is dropped or re-created during the execution of the application each time, but now the data is retained after database changes.

Step 1: Modify your Configuration.cs with the following code:
namespace Vag_Infotech.Migrations 
{ 
    using System; 
    using System.Collections.Generic; 
    using System.Data.Entity; 
    using System.Data.Entity.Migrations; 
    using System.Linq; 
    using Vag_Infotech.Models; 
  
    internal sealed class Configuration : DbMigrationsConfiguration<Vag_Infotech.DAL.CollegeDbContext> 
    { 
        public Configuration() 
        { 
            AutomaticMigrationsEnabled = false; 
        } 
  
        protected override void Seed(Vag_Infotech.DAL.CollegeDbContext context) 
        { 
            var New_Students = new List<Student> 
            { 
                new Student{FirstName="Alec",LastName="Michael", 
                    EnrollmentDate=DateTime.Parse("2009-07-01")}, 
                new Student{FirstName="Marie",LastName="Jane", 
                    EnrollmentDate=DateTime.Parse("2009-07-01")}, 
                new Student{FirstName="Peter",LastName="Parker", 
                    EnrollmentDate=DateTime.Parse("2009-07-05")}, 
                new Student{FirstName="Tony",LastName="Stark", 
                    EnrollmentDate=DateTime.Parse("2009-10-01")}, 
                new Student{FirstName="Steve",LastName="Rogers", 
                    EnrollmentDate=DateTime.Parse("2010-07-01")}, 
                new Student{FirstName="Natasha",LastName="Romanoff", 
                    EnrollmentDate=DateTime.Parse("2010-07-10")}, 
                new Student{FirstName="Bruce",LastName="Banner", 
                    EnrollmentDate=DateTime.Parse("2009-09-01")}, 
                new Student{FirstName="Scott",LastName="Lang", 
                    EnrollmentDate=DateTime.Parse("2009-08-05")}, 
            }; 
            New_Students.ForEach(ns => context.Students.AddOrUpdate(p => p.LastName, ns)); 
            context.SaveChanges(); 
  
            var New_Courses = new List<Course> 
            { 
                new Course{CourseID=201,Name="MCA",Credit=3,}, 
                new Course{CourseID=202,Name="M.Sc.IT",Credit=2,}, 
                new Course{CourseID=203,Name="M.Tech.CS",Credit=2,}, 
                new Course{CourseID=204,Name="M.Tech.IT",Credit=4,} 
            }; 
            New_Courses.ForEach(ns => context.Courses.AddOrUpdate(p => p.Name, ns)); 
            context.SaveChanges(); 
  
            var New_Enrollments = new List<Enrollment> 
            { 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Alec").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="MCA").CourseID, 
                    Grade=StudentGrade.A 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Marie").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="MCA").CourseID, 
                    Grade=StudentGrade.A 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Marie").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="M.Tech.IT").CourseID, 
                    Grade=StudentGrade.B 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Peter").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="M.Sc.IT").CourseID, 
                    Grade=StudentGrade.A 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Tony").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="MCA").CourseID, 
                    Grade=StudentGrade.A 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Tony").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="M.Sc.IT").CourseID, 
                    Grade=StudentGrade.B 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Steve").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="M.Tech.IT").CourseID, 
                    Grade=StudentGrade.A 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Natasha").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="MCA").CourseID, 
                    Grade=StudentGrade.B 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Bruce").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="M.Tech.IT").CourseID, 
                    Grade=StudentGrade.B 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Scott").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="MCA").CourseID, 
                    Grade=StudentGrade.A 
                }, 
                new Enrollment{ 
                    StudentID= New_Students.Single(ns=>ns.FirstName=="Scott").ID, 
                    CourseID=New_Courses.Single(nc=>nc.Name=="M.Tech.IT").CourseID, 
                    Grade=StudentGrade.D 
                }, 
            }; 
  
            foreach (Enrollment et in New_Enrollments) 
            { 
                var NewEnrollDb = context.Enrollments.Where( 
                    ns => ns.Student.ID == et.StudentID && 
                        ns.Course.CourseID == et.CourseID).SingleOrDefault(); 
                if (NewEnrollDb == null) 
                { 
                    context.Enrollments.Add(et); 
                } 
            } 
            context.SaveChanges(); 
        } 
    } 
}

In the code above the Seed() takes the context object as an input argument and in the code the object is used to add the entities to the database. We can see how the code creates the collection for the database for each entity type and then saves it by SaveChanges() and adds it through the DbSet property. It is not necessary to call the SaveChanges() after each group of entities.

Step 2: Build the solution.

Migration Executing

Step 1: Enter the following command in the Package Manager Console:

update-database

Step 2: Run the application and see the changes in the Students link.