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Validate Blank TextBox using CustomValidator in ASP.Net

In this blog we will know how to validate blank textbox using CustomValidator in ASP.Net.

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Blank__textbox_CustomValidator._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">

<head id="Head1" runat="server">

    <title>Untitled Page</title>

</head>

<body>

    <form id="form1" runat="server">

    <div>

        <div>

            <asp:Label ID="lblName" Text="Name:" AssociatedControlID="txtName" runat="server" />

            <br />

            <asp:TextBox ID="txtName" runat="server" />

            <asp:CustomValidator ID="cv_name" runat="server" ControlToValidate="txtName" Text="Name should not be blank"

                ValidateEmptyText="true" OnServerValidate="cv_name_ServerValidate"></asp:CustomValidator><br />

            <asp:Button ID="btnSubmit" Text="Submit" runat="server" />

        </div>

    </div>

    </form>

</body>

</html>

.CS Code
 

using System;

using System.Collections;

using System.Configuration;

using System.Data;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

 

namespace Blank__textbox_CustomValidator

{

    public partial class _Default : System.Web.UI.Page

    {

 

        protected void cv_name_ServerValidate(object source, ServerValidateEventArgs args)

        {

            if (args.Value.Length != 0)

                args.IsValid = true;

            else

                args.IsValid = false;

        }

    }

}