Calling JavaScript Client Side Validation function and Server side function

There is a attribute so called onClientClick you have to set that on your button click.

 <script type="text/javascript">
        function func1() {
            alert("the function called");
         }            
    </script>

    <asp:Button runat="server" Text="Button1" onclick="Unnamed1_Click" OnClientClick="func1()" CommandArgument="WithData"/>

One more thing to inform you is that if this fuction is returning false i.e return false; is coded in the function than the button would not cause to calle the server side event.

Hi, I understand above concept. Now i have one problem that is where the javascript  client code write in masterpage content form. I write the code in following manner <%@ Page Language="C#" MasterPageFile="~/CRM.master" AutoEventWireup="true" CodeFile="Complaint.aspx.cs" Inherits="Complaint" Title="Untitled Page" %> <asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server"> </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server"> <script type="text/javascript"> function ValidatePhone() { var txt_Phone=document.getElementById("txt_Phone").value; var regularExpression= /^[0-9]{10,}/; if (!txt_Phone.match(regularExpression)) {     alert("Please enter 10 digit mobile number");     return false; } else     return true; } </script> <asp:TextBox ID="txt_Description" runat="server" Width="185px" Height="51px"             TextMode="MultiLine"></asp:TextBox>         <asp:RequiredFieldValidator ID="Valid_Description" runat="server"             ControlToValidate="txt_Description" ErrorMessage="*"></asp:RequiredFieldValidator>  <asp:TextBox ID="txt_Phone" runat="server" Height="25px" Width="186px"></asp:TextBox>         <asp:RequiredFieldValidator ID="Valid_Phone" runat="server"             ControlToValidate="txt_Phone" ErrorMessage="*"></asp:RequiredFieldValidator> <asp:Button ID="btn_Submit" runat="server" Text="Submit"             onclick="btn_Submit_Click" OnClientClick="return ValidatePhone() /> </asp:Content> My problem is the javascript is not ckecking to validate. Please Guide me what problem is the above code

Ok.., But I would request you to initialize a new thread,  for this Question and IT IS HEIGHLY RECOMMANDED TO ALWAYS USE ADD CODE BUTTON TO PASTE ANY KIND OF CODE ELSE OTHER WISE IT MAY BE DELETED.

<asp:TextBox ID="txt_Phone" runat="server" Height="25px" Width="186px"></asp:TextBox>

in your above coding  line , u add  this ClientIDMode ="Static" ...

Why can't you use ajax tool kit regular expression validator?