ต้องการ alert หลังจาก update เสร็จแล้ว ว่าได้ทำการ update ข้อมูลเรียบร้อยแล้วค่ะ asp.net c#

using Microsoft.VisualBasic;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
partial class _Default : System.Web.UI.Page
{


	protected void Page_Load(object sender, System.EventArgs e)
	{
		string myscript = "alert(document.getElementById('TextBox1').value);";
		Page.ClientScript.RegisterStartupScript(this.GetType(), "myscript", myscript, true);
	}

	protected void Button1_Click(object sender, System.EventArgs e)
	{
		string strMessage = null;
		strMessage = "Hi, You clicked ClickMe button";
		//finishes server processing, returns to client.
		string strScript = "<script language=JavaScript>";
		strScript += "alert(\"" + strMessage + "\");";
		strScript += "</script>";

		if ((!ClientScript.IsStartupScriptRegistered("clientScript"))) {
			ClientScript.RegisterClientScriptBlock(this.GetType(), "clientScript", strScript);
		}

	}
}