how to match expression with textbox in asp.net

There are many ways to match the expression in textbox:

1) Write Server-side code to match
2) Declare a RegularExpressionValidator for the textbox
3) Use Javascript

1) Server side code:

using System;
using System.Text.RegularExpressions;

    void CheckTextBoxValue()
    {
	// First we see the input string.
	string input = TextBox1.text;
	// Here we call Regex.Match.
	Match match = Regex.Match(input, @"^[0-9]{10}$",
	    RegexOptions.IgnoreCase);
	// Here we check the Match instance.
	if (match.Success)
	{
	    // Finally Write your relevant code here.
	}
    }

2) RegularExpressionValidator: This is an example. Please make your changes accordingly.

<asp:textbox id="TextBox1" runat="server" validationgroup="check" xmlns:asp="#unknown"></asp:textbox>
<asp:regularexpressionvalidator id="RegularExpressionValidator1" runat="server" controltovalidate="TextBox1" xmlns:asp="#unknown">
ErrorMessage="Please Enter Only Numbers" ValidationExpression="^\d+$" ValidationGroup="check"></asp:regularexpressionvalidator>

3) Using Javascript:

function check(){
var re5digit=/^\d{5}$/ //regular expression defining a 5 digit number
if (document.myform.myinput.value.search(re5digit)==-1) //if match failed
alert("Please enter a valid 5 digit number inside form")
}

<form name="myform">
<input type="text" name="myinput" size=15>
<input type="button" onClick="check()" value="check">

</form>