ASP.NET MVC Input Validation

Validation of user input is necessary task for the application programmer. An application should allow only valid user input so that we get only desired information.

ASP.NET MVC framework provides built-in annotations that we can apply on Model properties. It validates input and display appropriate message to the user.

Commonly used Validation Annotations

Annotations	Description
Required	It is used to make a required field.
DisplayName	It is used to define the text we want to display for the fields.
StringLength	It defines a maximum length for a string field.
Range	It is used to set a maximum and minimum value for a numeric field.
Bind	It lists fields to exclude or include when binding parameter or form values to model properties.
ScaffoldColumn	It allows hiding fields from editor forms.
MaxLength	It is used to set max length for a field.
EmailAddress	It is used to validate email address.
DataType	It is used to specify data type for the field.
RegularExpression	It is used to associate regular expression for a field.

Example

Let’s create an example that will validate input by using the annotations. To create the example, first we are creating a StudentsController and then a Student Model.

Controller

// StudentsController.cs

  using System;  using System.Collections.Generic;  using System.Linq;  using System.Web;  using System.Web.Mvc;  namespace MvcApplicationDemo.Controllers  {      public class StudentsController : Controller      {          // GET: Students          public ActionResult Index()          {              return View();          }      }  }  

Model

// Student.cs

  using System.ComponentModel.DataAnnotations;    namespace MvcApplicationDemo.Models  {      public class Student      {          public int ID { get; set; }          // — Validating Student Name          [Required(ErrorMessage =”Name is required”)]          [MaxLength(12)]          public string Name { get; set; }          // — Validating Email Address          [Required(ErrorMessage =”Email is required”)]          [EmailAddress(ErrorMessage = “Invalid Email Address”)]          public string Email { get; set; }          // — Validating Contact Number          [Required(ErrorMessage = “Contact is required”)]          [DataType(DataType.PhoneNumber)]          [RegularExpression(@”^(?([0-9]{3}))?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$”, ErrorMessage = “Not a valid Phone number”)]          public string Contact { get; set; }      }  }  

View

// Index.cshtml

  @model MvcApplicationDemo.Models.Student  @{      ViewBag.Title = “Index”;  }  <h2>Index</h2>  @using (Html.BeginForm())   {      @Html.AntiForgeryToken()      <div class=”form-horizontal”>          <h4>Student</h4>          <hr />          @Html.ValidationSummary(true, “”, new { @class = “text-danger” })          <div class=”form-group”>              @Html.LabelFor(model => model.Name, htmlAttributes: new { @class = “control-label col-md-2″ })              <div class=”col-md-10”>                  @Html.EditorFor(model => model.Name, new { htmlAttributes = new { @class = “form-control” } })                  @Html.ValidationMessageFor(model => model.Name, “”, new { @class = “text-danger” })              </div>          </div>          <div class=”form-group”>              @Html.LabelFor(model => model.Email, htmlAttributes: new { @class = “control-label col-md-2″ })              <div class=”col-md-10”>                  @Html.EditorFor(model => model.Email, new { htmlAttributes = new { @class = “form-control” } })                  @Html.ValidationMessageFor(model => model.Email, “”, new { @class = “text-danger” })              </div>          </div>          <div class=”form-group”>              @Html.LabelFor(model => model.Contact, htmlAttributes: new { @class = “control-label col-md-2″ })              <div class=”col-md-10”>                  @Html.EditorFor(model => model.Contact, new { htmlAttributes = new { @class = “form-control” } })                  @Html.ValidationMessageFor(model => model.Contact, “”, new { @class = “text-danger” })              </div>          </div>          <div class=”form-group”>              <div class=”col-md-offset-2 col-md-10″>                  <input type=”submit” value=”Create” class=”btn btn-default” />              </div>          </div>      </div>  }  <div>      @Html.ActionLink(“Back to List”, “Index”)  </div>  @section Scripts {      @Scripts.Render(“~/bundles/jqueryval”)  }  

Output:

To see the output, right click on the Index.cshtml file and select view in browser. This will produce the following result.

As we can see that it validates form fields and display error message to the user. In the below screenshot, we are validating that the entered data is as expected.

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ASP.Net MVC Validation