ASP.NET MVC: Data Annotations for Model Validation

Data validation is a key aspect for developing web application. In Asp.net MVC, we can easily apply validation to web application by using Data Annotation attribute classes to model class. Data Annotation attribute classes are present in System.ComponentModel.DataAnnotations namespace and are availlable to Asp.net projects like Asp.net web application & website, Asp.net MVC, Web forms and also to Entity framework orm models.

Data Annotations help us to define the rules to the model classes or properties for data validation and displaying suitable messages to end users.

Data Annotation Validator Attributes

1. DataType

   Specify the datatype of a property
   

2. DisplayName

   specify the display name for a property.
   

3. DisplayFormat

   specify the display format for a property like different format for Date proerty.
   

4. Required

   Specify a property as required.
   

5. ReqularExpression

   validate the value of a property by specified regular expression pattern.
   

6. Range

   validate the value of a property with in a specified range of values.
   

7. StringLength

   specify min and max length for a string property.
   

8. MaxLength

   specify max length for a string property.
   

9. Bind

   specify fields to include or exclude when adding parameter or form values to model properties.
   

10. ScaffoldColumn

    specify fields for hiding from editor forms.
    
11. Url   Validates that a valid URL has been supplied as a property value

Designing the model with Data Annotations

 
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Web.Mvc;
namespace Employee.Models
{
 [Bind(Exclude = "EmpId")]
 public class Employee
 {
 [ScaffoldColumn(false)]
 public int EmpId { get; set; }
 
 [DisplayName("Employee Name")]
 [Required(ErrorMessage = "Employee Name is required")]
 [StringLength(100,MinimumLength=3)]
 public String EmpName { get; set; } 
 
 [Required(ErrorMessage = "Employee Address is required")] 
 [StringLength(300)]
 public string Address { get; set; } 
 
 [Required(ErrorMessage = "Salary is required")] 
 [Range(3000, 10000000,ErrorMessage = "Salary must be between 3000 and 10000000")]
 public int Salary{ get; set; } 
 
 [Required(ErrorMessage = "Please enter your email address")] 
 [DataType(DataType.EmailAddress)]
 [Display(Name = "Email address")]
 [MaxLength(50)]
 [RegularExpression(@"[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}", ErrorMessage = "Please enter correct email")]
 public string Email { get; set; }
 }
}

Once we have define validation to the model by using data annotations, these are automatically used by Html Helpers in views. For client side validation to work, please ensure that below two <SCRIPT> tag references are in the view.

 <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> 
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script> 

Presenting the model in the view

 @model Employee.Models
@{ 
 ViewBag.Title = "Employee Details"; 
 Layout = "~/Views/Shared/_Layout.cshtml";
 }
 @using (Html.BeginForm())
 {
 <div class="editor-label">
 @Html.LabelFor(m => m.EmpName)
 </div>
 <div class="editor-field"> 
 @Html.TextBoxFor(m => m.EmpName) 
 @Html.ValidationMessageFor(m => m.EmpName)
 </div> 
 <div class="editor-label">
 @Html.LabelFor(m => m.Address)
 </div> 
 <div class="editor-field">
 @Html.TextBoxFor(m => m.Address) 
 @Html.ValidationMessageFor(m => m.Address)
 </div> 
 <div class="editor-label"> 
 @Html.LabelFor(m => m.Salary)
 </div> 
 <div class="editor-field"> 
 @Html.TextBoxFor(m => m.Salary) 
 @Html.ValidationMessageFor(m => m.Salary)
 </div> 
 <div class="editor-label">
 @Html.LabelFor(m => m.Email)
 </div> 
 <div class="editor-field"> 
 @Html.TextBoxFor(m => m.Email) 
 @Html.ValidationMessageFor(m => m.Email)
 </div> 
 <p> <input type="submit" value="Save" />
 </p>
} 

Refeerence: http://www.dotnet-tricks.com/Tutorial/mvc/D8I4270712-MVC-Data-Annotations-for-Model-Validation.html