Regular Expression Validator In ASP.NET Web Forms | Form Validation | ASP.NET

 using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

namespace VALIDATION_CONTROLS

{

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

    {

        protected void Page_Load(object sender, EventArgs e)

        {

        }

        protected void Button1_Click(object sender, EventArgs e)

        {

            Page.ClientScript.RegisterStartupScript(this.GetType(),"Scripts","<script>alert('YOUR FORM HAS BEEN SUBMITTED !!')</script>");

        }

    }

}

Above File is VALIDATION_CONTROLS\VALIDATION_FORM.aspx.cs