JavaScript Alert box not being displayed using Response.Write in ASP.Net

i m using an alert box on click of the button and after alert box i am redirecting it to the other page.

the page is getting redirected without displaying the alert box. 

please also tell how to use message box in asp.net c#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class Default6 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
       
    }



    protected void btnAlert_Click(object sender, EventArgs e)
    {
        /*btnAlert.Attributes.Add("onclick", "javascript:alert('Invalid');");*/
        Response.Write("<script>alert('New Password is created')</script>");
       // Response.Redirect("web3.aspx");
    }
        
}

please reply