In this article, i help you to learn how to use Fluent Validation in ASP.NET MVC 5 implementation. Fluent validation is one way to set up dedicated validator objects, that you would use when you want to separate validation logic from business logic. Fluent validation contains a small validation library for .NET that uses a Fluent interface and lambda expressions for building validation rules for our business objects.

So, let's start using Fluent Validation!

Step 1:  Create a ASP.NET Application using MVC Template

First, click on "Tools" , choose "Library Package Manager" then "Package Manager Console" and type this following command:

install-package FluentValidation

Step 2: Lets create a Model class with the properties

namespace samplefluentvalidation.Models
{
    public class Products
    {
        public int ProductID { get; set; }
        public string ProductName { get; set; }
        public string ProductManufacturer { get; set; }
    }
}

Step 3:  Now lets Create a controller

using FluentValidation.Results;
using samplefluentvalidation.Models;
using samplefluentvalidation.Models.Validations;
using System.Web.Mvc;

namespace samplefluentvalidation.Controllers
{
    public class ProductsController : Controller
    {
        //
        // GET: /Products/
        public ActionResult Index()
        {
            return View();
        }
        [AcceptVerbs(HttpVerbs.Post)]
        public ActionResult Index(Products model)
        {
            ProductValidator validator = new ProductValidator();
            ValidationResult result = validator.Validate(model);
            if (result.IsValid)
            {
                ViewBag.ProductName = model.ProductName;
                ViewBag.ProductManufacturer = model.ProductManufacturer;
              
            }
            else
            {
                foreach (ValidationFailure failer in result.Errors)
                {
                    ModelState.AddModelError(failer.PropertyName, failer.ErrorMessage);
                }
            }
            return View(model);
        }
    }
}

Step 4:  Now create a folder named products in views

Add a view named Index and add the below lines:

@model samplefluentvalidation.Models.Products
@{
    ViewBag.Title = "Index";
}
@if (ViewData.ModelState.IsValid)
{
    <b>
       Product Name : @ViewBag.ProductName<br />
       Product Manufacturer : @ViewBag.ProductManufacturer
    </b>
}
@using (Html.BeginForm())
{
    <fieldset>
        <legend>Products</legend>
        <div class="editor-label">
            @Html.LabelFor(model => model.ProductName)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.ProductName)
            @Html.ValidationMessageFor(model => model.ProductName)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.ProductManufacturer)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.ProductManufacturer)
            @Html.ValidationMessageFor(model => model.ProductManufacturer)
        </div>
        <p>
            <input type="submit" value="Create" />
        </p>
    </fieldset>
}
@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

Now, we have created all the model controller. This view shows the index page and the validation check.

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