The construction of ASP.NET Core MVC web applications using controllers and views is covered in this lesson. There are various phases involved in implementing a star rating system using Dapper in.NET Core. To save ratings, you must first configure your database schema. Next, in order to communicate with the database, you'll need to establish the Dapper repository and the required model classes.

What is Rate Yo?
Rate Yo is a free, tiny, and flexible jQuery star rating plugin, it uses SVG to generate an image and render rating, so no images are required.

Prerequisites

• Visual Studio is the latest version with the ASP.NET and web development workload.
• .NET SDK latest version (.NET 8.0)
• SQL SERVER latest

Making a table in a database
Start SQL Server, choose Database, then click Create New Database.

CREATE TABLE [dbo].[t_company_rating]
(
    [f_uid]              UNIQUEIDENTIFIER PRIMARY KEY NOT NULL,
    [f_iid]              INT              IDENTITY (1, 1) NOT NULL,
    [f_company_name]     NVARCHAR (100)   NULL,
    [f_company_location] NVARCHAR (100)   NULL,
    [f_country]          NVARCHAR (100)   NULL,
    [f_glassdoor_rating] FLOAT (53)       NULL,
)

Starting a New Visual Studio Project
Open Visual Studio, then choose File > New Project.

Make a Web Application

• Launch Visual Studio, then choose File > New Project
• Select the ASP.NET Core Web App (Model-View-Controller) > Next option from the Create a new project dialog box

Setting Up Your New Project
Enter RatingSystem_Demo as the project name in the Configure your new project dialog.

• The project should be named RatingSystem_Demo. When copying code, capitalization must match each namespace.
• Select a place to work on your project.
• Name the solution.
• Click on Next.

Additional information
In the Additional information dialog.

• Select .NET 8.0 (Long Term Support).
• Verify that Do not use top-level statements is unchecked.
• Select Create.

Option 1. Install the Dapper, Microsoft.Data.SqlClient Library through NuGet Package Manager

• Go to Project > Manage NuGet Packages.
• On the NuGet Package Manager page, select nuget.org as the Package source.
• Under the Browse tab, search for Dapper, then choose Dapper from the list and select Install.
• If prompted to verify the installation, click OK.

Option 2: Using the Visual Studio Command Line to install the Dapper Library
Go to Tools > NuGet Package Manager > Package Manager Console in Visual Studio.
Under the Package Manager Console tab, type the following command.
Install-Package Dapper

Add RateYo library files

Library files can be added to an ASP.NET Core project in two different ways.

• Use the Add Client-Side Library dialog
• Manually configure LibMan manifest file entries

Use the Add Client-Side Library dialog
Follow these steps to install a client-side library.
In Solution Explorer, right-click the project folder in which the files should be added. Choose Add > Client-Side Library. The Add Client-Side Library dialog appears.

Add Client-side Library

The suggested Target Location folder is based on the location from which the dialog is launched.
If launched from the project root.

• wwwroot/lib is used if wwwroot exists.
• lib is used if wwwroot doesn't exist.
• If launched from a project folder, the corresponding folder name is used.

The folder suggestion is suffixed with the library name. The following table illustrates folder suggestions when installing jQuery in a Razor Pages project.

Click the Install button to download the files, per the configuration in libman.json.

Add a data model class

Right-click the Models folder > Add > Class. Name the file CompanyModel.cs.
Replace the Models/CompanyModel.cs file with using c# following code.
The CompanyModel class contains a f_uid field, which is required by the database for the primary key.

CompanyModel.cs
using System.ComponentModel.DataAnnotations;

namespace RatingSystem_Demo.Models
{
    public class CompanyModel
    {
        public Guid f_uid { get; set; }

        [Display(Name ="ID")]
        public int f_iid { get; set; }

        [Display(Name = "Company Name")]
        public string f_company_name { get; set; }

        [Display(Name = "Location")]
        public string f_company_location { get; set; }

        [Display(Name = "Country")]
        public string f_country { get; set; }

        [Display(Name = "Glassdoor Rating")]
        public float f_glassdoor_rating { get; set; }
    }
}

Adding interfaces

• In Solution Explorer, right-click Add New Folder.
• Rename the folder to Repositories.
• Right-click on the renamed folder and Add the interface name IGenericRepository.cs

IGenericRepository.cs
namespace RatingSystem_Demo.Repositories
{
    public interface IGenericRepository<T> where T : class
    {
        Task<IEnumerable<T>> Get();
        Task<T> Find(Guid uid);
        Task<T> Add(T model);
        Task<T> Update(T model);
        Task<T> Remove(T model);
    }
}

IUnitOfWork.cs
namespace RatingSystem_Demo.Repositories
{
    public interface IUnitOfWork
    {
        ICompany Companies { get; }
    }
}

ICompany.cs
using RatingSystem_Demo.Models;

namespace RatingSystem_Demo.Repositories
{
    public interface ICompany:IGenericRepository<CompanyModel>
    {

    }
}

Interface Implementation
UnitOfWork.cs
namespace RatingSystem_Demo.Repositories
{
    public class UnitOfWork : IUnitOfWork
    {
        public ICompany Companies { get; set; }
        public UnitOfWork(ICompany Companies)
        {
            this.Companies = Companies;
        }
    }
}

CompanyRepository.cs
using Dapper;
using Microsoft.Data.SqlClient;
using RatingSystem_Demo.Models;

namespace RatingSystem_Demo.Repositories
{
    public class CompanyRepository : ICompany
    {
        private readonly IConfiguration _configuration;
        private readonly SqlConnection _connection;
        public CompanyRepository(IConfiguration configuration)
        {
            _configuration = configuration;
            _connection = new SqlConnection(_configuration.GetConnectionString("DefaultConnection"));
        }
        public async Task<IEnumerable<CompanyModel>> Get()
        {
            var sql = $@"
                        SELECT [f_uid]
                              ,[f_iid]
                              ,[f_company_name]
                              ,[f_company_location]
                              ,[f_country]
                              ,[f_glassdoor_rating]
                          FROM
                               [Sample-DB].[dbo].[t_company_rating]
                               ORDER BY f_iid ASC";

            return await _connection.QueryAsync<CompanyModel>(sql);
        }
        public async Task<CompanyModel> Find(Guid uid)
        {
            var sql = $@"
                        SELECT [f_uid]
                              ,[f_iid]
                              ,[f_company_name]
                              ,[f_company_location]
                              ,[f_country]
                              ,[f_glassdoor_rating]
                          FROM [Sample-DB].[dbo].[t_company_rating]
                          WHERE
                               [f_uid]=@uid";

            return await _connection.QueryFirstOrDefaultAsync<CompanyModel>(sql, new { uid });
        }
        public async Task<CompanyModel> Add(CompanyModel model)
        {
            model.f_uid = Guid.NewGuid();

            var sql = $@"
                     INSERT INTO [dbo].[t_company_rating]
                           ([f_uid]
                           ,[f_company_name]
                           ,[f_company_location]
                           ,[f_country]
                           ,[f_glassdoor_rating])
                     VALUES
                           (@f_uid,
                            @f_company_name,
                            @f_company_location,
                            @f_country,
                            @f_glassdoor_rating)";

            await _connection.ExecuteAsync(sql, model);
            return model;
        }
        public async Task<CompanyModel> Update(CompanyModel model)
        {
            var sql = $@"UPDATE [dbo].[t_company_rating]
                        SET
                            [f_company_name] = @f_company_name,
                            [f_company_location] = @f_company_location,
                            [f_country] = @f_country,
                            [f_glassdoor_rating] = @f_glassdoor_rating
                         WHERE
                            f_uid=@f_uid";

            await _connection.ExecuteAsync(sql, model);
            return model;
        }
        public async Task<CompanyModel> Remove(CompanyModel model)
        {
            var sql = $@"
                        DELETE FROM
                            [dbo].[t_company_rating]
                        WHERE
                            [f_uid]=@f_uid";

            await _connection.ExecuteAsync(sql, model);
            return model;
        }
    }
}

Add a controller

• In Solution Explorer, right-click Controllers > Add > Controller.
• In the Add New Scaffolded Item dialog box, select MVC Controller - Empty > Add.
• In the Add New Item - RatingSystem_Demo dialog, enter CompaniesController.cs and select Add.

Replace the contents of Controllers/CompaniesController.cs with the following code.
using Microsoft.AspNetCore.Mvc;
using RatingSystem_Demo.Models;
using RatingSystem_Demo.Repositories;

namespace RatingSystem_Demo.Controllers
{
    public class CompaniesController : Controller
    {
        private readonly IUnitOfWork unitOfWork;
        public CompaniesController(IUnitOfWork unitOfWork)
        {
            this.unitOfWork = unitOfWork;
        }
        public async Task<IActionResult> Index()
        {
            var companies = await unitOfWork.Companies.Get();
            var ratings = companies.Select(x => x.f_glassdoor_rating).ToList();
            ViewBag.Ratings = string.Join(", ", ratings);
            return View(companies);
        }
        public async Task<IActionResult> Details(Guid id)
        {
            var company = await unitOfWork.Companies.Find(id);
            return View(company);
        }

        public IActionResult Create()
        {
            return View();
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Create(CompanyModel model)
        {
            var company = await unitOfWork.Companies.Add(model);
            return RedirectToAction(nameof(Index));
        }

        [HttpGet]
        public async Task<IActionResult> Edit(Guid id)
        {
            if (id == Guid.Empty)
            {
                return NotFound();
            }
            var company = await unitOfWork.Companies.Find(id);
            if (company == null)
            {
                return BadRequest();
            }
            return View(company);
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> Edit(Guid id, CompanyModel model)
        {
            if (id == Guid.Empty)
            {
                return NotFound();
            }
            var company = await unitOfWork.Companies.Find(id);
            if (company == null)
            {
                return BadRequest();
            }
            await unitOfWork.Companies.Update(model);
            return RedirectToAction(nameof(Index));
        }
        public async Task<IActionResult> Delete(Guid id)
        {
            if (id == Guid.Empty)
            {
                return NotFound();
            }
            var company = await unitOfWork.Companies.Find(id);
            if (company == null)
            {
                return BadRequest();
            }
            return View(company);
        }

        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> ConfirmDelete(Guid id)
        {
            var company = await unitOfWork.Companies.Find(id);
            await unitOfWork.Companies.Remove(company);
            return RedirectToAction(nameof(Index));
        }
    }
}

Add a view

• Right-click on the Views folder, then Add > New Folder, and name the folder Companies
• Right-click on the Views/Companies folder, and then Add > New Item.
• In the Add New Item dialog, select Show All Templates.
• In the Add New Item - RatingSystem_Demo dialog:
• In the search box in the upper-right, enter the view
• Select Razor View - Empty
• Keep the Name box value, Index.cshtml.
• Select Add

Replace the contents of the Views/Companies/Index.cshtml, Create.cshtml, Edit.cshtml and Delete.cshtml Razor view file with the following:

Index.cshtml
@model IEnumerable<RatingSystem_Demo.Models.CompanyModel>

@{
    ViewData["Title"] = "Index";
}

<h4 class="text-uppercase text-center">List of companies</h4>

<p style="float:right"><a asp-action="Create" class="btn btn-primary btn-md rounded-0"><i class="fa-solid fa-plus"></i> Add New</a></p>
<table class="table table-bordered table-striped">
    <thead>
        <tr>
            <th>@Html.DisplayNameFor(model => model.f_iid)</th>
            <th>@Html.DisplayNameFor(model => model.f_company_name)</th>
            <th>@Html.DisplayNameFor(model => model.f_company_location)</th>
            <th>@Html.DisplayNameFor(model => model.f_country)</th>
            <th>@Html.DisplayNameFor(model => model.f_glassdoor_rating)</th>
            <th>Action(s)</th>
        </tr>
    </thead>
    <tbody>
        @foreach (var item in Model) {
        <tr>
            <td>@item.f_iid</td>
            <td><a style="text-decoration:none" href="@Url.Action("Details","Companies", new { id = item.f_uid })">@item.f_company_name</a></td>
            <td>@item.f_company_location</td>
            <td>@item.f_country</td>
            <td>
                <span style="float:left;display:inline">@item.f_glassdoor_rating <span style="float:left;display:inline" class="rateYo"></span></span>
            <td>
                <a href="@Url.Action("Edit","Companies", new { id = item.f_uid })" class="btn btn-info btn-sm rounded-0"><i class="fa-solid fa-pen-to-square"></i></a>
                <a href="@Url.Action("Delete","Companies", new { id = item.f_uid })" class="btn btn-danger btn-sm rounded-0"><i class="fa-solid fa-trash"></i></a>
            </td>
        </tr>
}
    </tbody>
</table>
@section Scripts {
    @{
        await Html.RenderPartialAsync("_ValidationScriptsPartial");
    }
    <script type="text/javascript">
        $(function () {
             var demoRatings = [@ViewBag.Ratings],
            stars = $('.rateYo');
            for (var i = 0; i < stars.length; i++) {
                $('.rateYo').eq(i).rateYo({
                    rating: demoRatings[i],
                    readOnly: true
                });
            }
        });
    </script>
}

Create.cshtml
@model RatingSystem_Demo.Models.CompanyModel

@{
    ViewData["Title"] = "Create";
}
<div class="container">
    <div class="card">
        <div class="card-header">
            <h4>Compnay</h4>
        </div>
        <div class="card-body">
            <div class="row">
                <div class="col-md-4">
                    <form asp-action="Create">
                        <div asp-validation-summary="ModelOnly" class="text-danger"></div>
                        <div class="form-group">
                            <label asp-for="f_company_name" class="control-label"></label>
                            <input asp-for="f_company_name" class="form-control" />
                            <span asp-validation-for="f_company_name" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <label asp-for="f_company_location" class="control-label"></label>
                            <input asp-for="f_company_location" class="form-control" />
                            <span asp-validation-for="f_company_location" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <label asp-for="f_country" class="control-label"></label>
                            <input asp-for="f_country" class="form-control" />
                            <span asp-validation-for="f_country" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <label asp-for="f_glassdoor_rating" class="control-label"></label>
                            <input asp-for="f_glassdoor_rating" readonly class="form-control counter" />
                            <br />
                            <div id="rateYo"></div>
                            <br />
                            <span asp-validation-for="f_glassdoor_rating" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <input type="submit" value="Save" class="btn btn-primary btn-md rounded-0" />
                            <a asp-action="Index" class="btn btn-primary btn-md rounded-0"><i class="fa-solid fa-backward"></i>Back to List </a>
                        </div>
                    </form>
                </div>
            </div>
        </div>
     </div>
</div>

@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
    <script>
        $(function () {
            $("#rateYo").rateYo({
                onChange: function (rating, rateYoInstance) {
                    $("#f_glassdoor_rating").val(rating);
                }
            });
        });
    </script>
}

Edit.cshtml
@model RatingSystem_Demo.Models.CompanyModel

@{
    ViewData["Title"] = "Edit";
}

<div class="container">
    <div class="card">
        <div class="card-header">
            <h4>Compnay</h4>
        </div>
        <div class="card-body">
            <div class="row">
                <div class="col-md-4">
                    <form asp-action="Edit">
                        <div asp-validation-summary="ModelOnly" class="text-danger"></div>
                        <input hidden asp-for="f_uid" />
                        <input hidden asp-for="f_iid" />
                        <div class="form-group">
                            <label asp-for="f_company_name" class="control-label"></label>
                            <input asp-for="f_company_name" class="form-control" />
                            <span asp-validation-for="f_company_name" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <label asp-for="f_company_location" class="control-label"></label>
                            <input asp-for="f_company_location" class="form-control" />
                            <span asp-validation-for="f_company_location" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <label asp-for="f_country" class="control-label"></label>
                            <input asp-for="f_country" class="form-control" />
                            <span asp-validation-for="f_country" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <label asp-for="f_glassdoor_rating" class="control-label"></label>
                            <input asp-for="f_glassdoor_rating" readonly class="form-control counter" />
                            <br />
                            <div id="rateYo"></div>
                            <br />
                            <span asp-validation-for="f_glassdoor_rating" class="text-danger"></span>
                        </div>
                        <div class="form-group">
                            <input type="submit" value="Save" class="btn btn-primary btn-md rounded-0" />
                            <a asp-action="Index" class="btn btn-primary btn-md rounded-0"><i class="fa-solid fa-backward"></i>Back to List </a>
                        </div>
                    </form>
                </div>
            </div>
        </div>
    </div>
</div>

@section Scripts {
    @{
        await Html.RenderPartialAsync("_ValidationScriptsPartial");
    }
    <script>
        $(function () {
            $("#rateYo").rateYo({
                rating: @Model.f_glassdoor_rating,
                onChange: function (rating, rateYoInstance) {
                    $("#f_glassdoor_rating").val(rating);
                }
            });
        });
    </script>
}

Delete.cshtml
@model RatingSystem_Demo.Models.CompanyModel

@{
    ViewData["Title"] = "Delete";
}

<div class="container">
    <div class="card">
        <div class="card-header">
            <h4>Compnay</h4>
        </div>
        <div class="card-body">
            <h5 class="alert alert-danger" role="alert">Are you sure you want to delete this?</h5>
            <dl class="row">
                <dt class="col-sm-2">
                    @Html.DisplayNameFor(model => model.f_iid)
                </dt>
                <dd class="col-sm-10">
                    @Html.DisplayFor(model => model.f_iid)
                </dd>
                <dt class="col-sm-2">
                    @Html.DisplayNameFor(model => model.f_company_name)
                </dt>
                <dd class="col-sm-10">
                    @Html.DisplayFor(model => model.f_company_name)
                </dd>
                <dt class="col-sm-2">
                    @Html.DisplayNameFor(model => model.f_company_location)
                </dt>
                <dd class="col-sm-10">
                    @Html.DisplayFor(model => model.f_company_location)
                </dd>
                <dt class="col-sm-2">
                    @Html.DisplayNameFor(model => model.f_country)
                </dt>
                <dd class="col-sm-10">
                    @Html.DisplayFor(model => model.f_country)
                </dd>
                <dt class="col-sm-2">
                    @Html.DisplayNameFor(model => model.f_glassdoor_rating)
                </dt>
                <dd class="col-sm-10">
                    <div id="rateYo"></div>
                </dd>
            </dl>
        </div>
        <div class="card-footer">
            <form asp-action="Delete">
                <button type="submit" class="btn btn-danger btn-sm rounded-0"><i class="fa-solid fa-trash"></i></button>
                <a asp-action="Index" class="btn btn-primary btn-sm rounded-0"><i class="fa-solid fa-backward"></i></a>
            </form>
        </div>
    </div>
</div>
@section Scripts {
    @{
        await Html.RenderPartialAsync("_ValidationScriptsPartial");
    }
    <script>
        $(function () {
            $("#rateYo").rateYo({
                rating: @Model.f_glassdoor_rating,
                readOnly: true
            });
        });
    </script>
}

Add repository services to the Program.cs
The object get method handles for example the task of connecting to the database and mapping Speaker objects to database records.
The database context get method is registered with the Dependency Injection container using the C# method, for example, the Program.cs file.
builder.Services.AddTransient<ICompany, CompanyRepository>();
builder.Services.AddTransient<IUnitOfWork, UnitOfWork>()

C#
Add Connection String

The ASP.NET Core Configuration system reads the DefaultConnection key. For local development, it gets the connection string from the appsettings.json file.

{
  "ConnectionStrings": {
    "DefaultConnection": "Data Source=farhan1086\\SQLEXPRESS;Initial Catalog=Sample-DB;Integrated Security=True;MultipleActiveResultSets=True;Encrypt=False;TrustServerCertificate=False;"
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning"
    }
  },
  "AllowedHosts": "*"
}

Run the Application
Select Ctrl+F5 to run the app without the debugger. Visual Studio runs the ASP.NET app and opens the default browser.

ASP.NET MVC enables developers to link server-side models and user interface elements with ease in the dynamic world of web development. In this process, model binding is essential, and data annotations offer a potent toolkit for specifying metadata about the features of the model. This blog offers a thorough how-to for ASP.NET MVC newcomers, with the goal of demystifying the relationship between model binding and data annotations.

The Model-View-Controller architectural pattern, which is used by ASP.NET MVC, has views handle display while controllers handle user input and coordinate interactions between views and models. Models contain data and business logic. The process by which user input from a form or other sources is used to populate the model properties is known as model binding.

On the other side, characteristics added to model properties to provide metadata about how they should be handled during model binding, validation, and rendering are known as data annotations.

Model Binding Basics
Consider a simple scenario where you have a Person model.

public class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public int Age { get; set; }
}

It may be desirable to connect user input to this model in a controller action.

[HttpPost]
public ActionResult SavePerson(Person person)
{
    // Process the person object
    // ...
}

Introducing Data Annotations
Now, let's enhance the Person model with data annotations to provide more information to the model binder.
public class Person
{
    [Required(ErrorMessage = "First Name is required")]
    [StringLength(50, ErrorMessage = "First Name should be less than 50 characters")]
    public string FirstName { get; set; }

    [Required(ErrorMessage = "Last Name is required")]
    [StringLength(50, ErrorMessage = "Last Name should be less than 50 characters")]
    public string LastName { get; set; }

    [Range(1, 150, ErrorMessage = "Age should be between 1 and 150")]
    public int Age { get; set; }
}

Important Data Annotations Employed

• Indicates that a certain attribute is necessary.
• StringLength: Indicates a string property's maximum length.
• Range: Indicates a numeric property's value range.

Making the Most of Data Annotations in Views

@using (Html.BeginForm("SavePerson", "YourController", FormMethod.Post))
{
    @Html.LabelFor(model => model.FirstName)
    @Html.TextBoxFor(model => model.FirstName)
    @Html.ValidationMessageFor(model => model.FirstName)

    // Repeat for LastName and Age properties

    <input type="submit" value="Save" />
}

Important HTML Helpers Employed

• The label element for a model attribute is rendered by LabelFor.
• Renders a text input element for a model attribute using TextBoxFor.
• ValidationMessageFor: Validation error messages for a model property rendered by the renderer.

In-Progress Model Validation
The model binder automatically validates the user input when the form is submitted by using the data annotations. Error notifications appear next to the respective form fields if any validation fails.

HTML helpers can be used to render form components in a view. Annotations on data affect the generation and validation of these elements.

Data Annotations' Advantages in Model Binding
Consistency: Data annotations offer a declarative and consistent means of defining validation criteria, guaranteeing consistency throughout the program.
Readability: Developers can readily comprehend the limitations and specifications of each property since validation rules are incorporated directly into the model.
Reuse: Data annotations facilitate code reuse by allowing the same model to be applied with identical validation rules across contexts.

Validating form data and processing user input are made easier using ASP.NET MVC model binding and data annotations. Developers can define validation criteria succinctly within the model itself by utilizing properties like Required, StringLength, and Range. This method makes code more readable, encourages consistency, and makes it easier to maintain reliable and user-friendly online applications. Embrace the power of model binding and data annotations as you begin your ASP.NET MVC adventure to build applications that are robust and user-friendly.

Cross-site Scripting, or PDF XSS, is another name for PDF Injection, which is a potentially dangerous security flaw. In an MVC (Model-View-Controller) application, it is imperative to include appropriate validation and sanitation techniques to prevent such difficulties during PDF upload and viewing. The sample code that shows how to handle PDF uploads safely and stop PDF Injection from causing Cross-site Scripting in an MVC environment is provided below.

Assuming you are working with a well-known MVC framework such as ASP.NET MVC, the following is a C# example that is simplified:

PDF Upload Validation: Implement server-side validation to ensure that only legitimate PDF files are accepted throughout the upload process.

[HttpPost]
public ActionResult UploadPdf(HttpPostedFileBase pdfFile)
{
    if (pdfFile != null && pdfFile.ContentLength > 0)
    {
        // Check if the uploaded file is a PDF
        if (pdfFile.ContentType != "application/pdf" || !pdfFile.FileName.EndsWith(".pdf"))
        {
            ModelState.AddModelError("pdfFile", "Only PDF files are allowed.");
            return View("Upload");
        }

        // Process the PDF file
        // ...
    }

    return RedirectToAction("Index");
}

Viewing a PDF: Use secure libraries that don't run any embedded JavaScript while rendering the PDF for viewing. Don't forget to sanitize the PDF's contents.

public ActionResult ViewPdf(int fileId)
{
    // Fetch the PDF file from the database or file system based on the fileId
    var pdfContent = GetPdfContent(fileId);

    // Sanitize the PDF content to prevent XSS
    var sanitizedPdfContent = SanitizePdfContent(pdfContent);

    // Render the sanitized PDF content
    return File(sanitizedPdfContent, "application/pdf");
}

Sanitizing PDF Content: To stop JavaScript from running, implement a function that sanitizes the PDF content.

private byte[] SanitizePdfContent(byte[] pdfContent)
{
    // Implement PDF content sanitization logic here
    // Check that the PDF content does not contain malicious scripts

    // Example: Using a library to remove JavaScript from the PDF content
    // var sanitizedContent = PdfSanitizationLibrary.Sanitize(pdfContent);

    // Return the sanitized PDF content
    // return sanitizedContent;

    // For illustration purposes, let's assume no sanitization for simplicity
    return pdfContent;
}

This is a rudimentary example; in a real-world situation, you might want to make sure that the PDF processing library is secure against PDF Injection and utilize a separate library. To reduce the danger of cross-site scripting (XSS) attacks, think about adding Content Security Policy (CSP) headers to your online application.

To take advantage of security updates and enhancements, make sure your libraries and frameworks are up to date at all times.

To sum up, strengthening your web environment begins with giving your MVC application's security first priority when it comes to PDF uploads. Strong validation checks put in place during the upload process create a strong initial line of defense against efforts at harmful PDF Injection. Choosing safe and up-to-date PDF rendering libraries reduces the possibility of Cross-site Scripting (XSS) vulnerabilities by guaranteeing that the material shown to users is free of malicious scripts. By including content sanitization procedures, a thorough defense against potential security threats is provided, adding an additional layer of protection.

It's critical to remain proactive as the digital landscape changes constantly. It is essential to keep your application's dependencies, such as PDF processing libraries, up to date in order to take advantage of the most recent security improvements. Your development lifecycle should include regular penetration tests and security assessments as they can assist find and fix new vulnerabilities. Following these guidelines will make your MVC application more resilient and help your users have a safer and more reliable online experience.