Data Annotations Validation in ASP.NET

This article explains how to use data annotations for validation in ASP.Net 4.5. So, let's proceed with the following
The effect of a custom validation message: Required, String Length, Data Type, Range, Compare and Regular Expression.

Creating a Registration Page

Create a new project using "File" -> "New" -> "Project..." then select web "ASP.NET Web Forms Application". Name it "DataAnnotationsValidation".
seelct New ASP.NET Project then select the template Empty and select Web Forms then click OK.
Next, create the code-behind as follows, displaying the validation errors to the users in the Registration.aspx.

Registration.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Registration.aspx.cs" Inherits="DataAnnotationsValidation.Registration" %> 
<!DOCTYPE html> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head runat="server"> 
    <title>Employees Registration</title> 
    <link href="Content/bootstrap.min.css" rel="stylesheet" /> 
</head> 
<body> 
    <form id="form1" runat="server"> 
        <div class="container"> 
            <div class="well"> 
                <h1>Data Annotations  Validation in ASP .NET 4.5 </h1> 
            </div> 
            <div class=" panel panel-default"> 
                <div class="panel-heading"> 
                    <h3 class="panel-title">Employees Registration</h3> 
                </div> 
                <div class="panel-body"> 
                    <div class="text-center"> 
                    <asp:ValidationSummary ID="validationSummary" runat="server" ShowModelStateErrors="true" DisplayMode="List" ForeColor="Red"  /> 
                    </div> 
                        <div class="col-md-8"> 
                            <div class="form-group col-lg-12"> 
                                <label>First Name</label> 
                                <asp:TextBox ID="FirstName" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-12"> 
                                <label>Last Name</label> 
                                <asp:TextBox ID="LastName" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-12"> 
                                <label>User ID</label> 
                                <asp:TextBox ID="UserID" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>Password </label> 
                                <asp:TextBox ID="Password" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>Password Confirm </label> 
                                <asp:TextBox ID="PasswordConfirm" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>Mobile </label> 
                                <asp:TextBox ID="Mobile" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>Age </label> 
                                <asp:TextBox ID="Age" runat="server" class="form-control"></asp:TextBox> 
                            </div>                             
                            <div class="form-group col-lg-6"> 
                                <label>Email </label> 
                                <asp:TextBox ID="Email" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>Email Confirm </label> 
                                <asp:TextBox ID="EmailConfirm" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>DOB </label> 
                                <asp:TextBox ID="Date" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>Salary </label> 
                                <asp:TextBox ID="Total" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>City </label> 
                                <asp:TextBox ID="HomeCity" runat="server" class="form-control"></asp:TextBox> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <label>Department </label> 
                                 
                                <asp:DropDownList ID="Department" runat="server" class="form-control"> 
                        <asp:ListItem Value="">Choose an Option</asp:ListItem>
                        <asp:ListItem Value="HR">HR</asp:ListItem> 
                        <asp:ListItem Value="Account">Account</asp:ListItem> 
                                    </asp:DropDownList> 
                            </div> 
                            <div class="form-group col-lg-6"> 
                                <asp:Button ID="btnsubmit" runat="server" Text="submit" /> 
                            </div> 
                        </div>                     
                </div> 
                </div> 
            </div> 
    </form> 
</body> 
</html>

Create DataAnnotationsValidation.Models for Validation
Now, do something with Models then click Add -> Class.
Applying validation attributes to the Validation class

Validation.cs

    using System; 
    using System.Collections.Generic; 
    using System.Linq; 
    using System.Web;   
    //using Namespace 
    using System.ComponentModel.DataAnnotations; 
    namespace DataAnnotationsValidation.Models 
    { 
        public class Validation 
        {         
            [Required] 
            [StringLength(120, MinimumLength = 3)] 
            public string FirstName { get; set; }  
            [Required] 
            [StringLength(120, MinimumLength = 3)] 
            public string LastName { get; set; } 
            [Required] 
            [StringLength(25, MinimumLength = 3)] 
            public string UserID { get; set; } 
            [Required] 
            [DataType(DataType.Password)] 
            public string Password { get; set; } 
            [Required] 
            [Compare("Password")] 
            public string PasswordConfirm { get; set; } 
            [Required] 
            [Range(18, 100, ErrorMessage = "Please enter an age between 18 and 50")] 
            public int Age { get; set; }   
            [Required]        
            [StringLength(10)] 
            public int Mobile { get; set; }           
            [RegularExpression(@"[A-Za-z0-9._%+-][email protected][A-Za-z0-9.-]+\.[A-Za-z]{2,4}", ErrorMessage = "Email doesn't look like a valid email address.")] 
            public string Email { get; set; }     
            [Compare("Email")] 
            public string EmailConfirm { get; set; }    
            [Range(typeof(decimal), "0.00", "15000.00")] 
            public decimal Total { get; set; }   
            [Required] 
            [DataType(DataType.Date)] 
            public DateTime Date { get; set; }       
            [Required] 
            public string HomeCity { get; set; }      
            [Required] 
            public string Department { get; set; }     
        } 
    } 

Next, create the code-behind as follows.

Registration.aspx.cs

    using System; 
    using System.Collections.Generic; 
    using System.Linq; 
    using System.Web; 
    using System.Web.UI; 
    using System.Web.UI.WebControls;     
    //using Namespace Models 
    using System.Web.ModelBinding; 
    using DataAnnotationsValidation.Models;    
    namespace DataAnnotationsValidation 
    { 
        public partial class Registration : System.Web.UI.Page 
        { 
            protected void Page_Load(object sender, EventArgs e) 
            { 
                if (IsPostBack) 
                { 
                    Validation v = new Validation(); 
                    if (TryUpdateModel(v, new FormValueProvider(ModelBindingExecutionContext))) 
                    { 
                        ShowMessage(v.ToString());                     
                    } 
                } 
            } 
            /// <summary> 
            /// This function is used for show message. 
            /// </summary> 
            /// <param name="msg"></param> 
            void ShowMessage(string msg) 
            { 
                ClientScript.RegisterStartupScript(Page.GetType(), "validation", "<script language='javascript'>alert('" + msg + "');</script>");
            }     
        } 
    }

Now run the page, it will look like the following to use validation to check the input.

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