Show MessageBox after successful operation in ASP.Net

Refer

thanks sir but i don't want something like that 

i want when users enter their data in page if their data be correct  and insert to database sucessfully after that it show massage but here when i click on button atfirst show massage after that below code worked.

rotected void ImageButton2_Click1(object sender, ImageClickEventArgs e)

Paste the code how you did it

  protected void Page_Load(object sender, EventArgs e)
    {



            string message = "Your request is being processed.";
            System.Text.StringBuilder sb = new System.Text.StringBuilder();
            sb.Append("alert('");
            sb.Append(message);
            sb.Append("');");
            ClientScript.RegisterOnSubmitStatement(this.GetType(), "alert", sb.ToString());

and this is my imagebutton code that i want when users click on it it show massage of course after insert data in database sucessfully

    protected void ImageButton2_Click1(object sender, ImageClickEventArgs e)
    {
        string data = Server.UrlDecode(Request.QueryString["BehCode"]);


            string price = RadioButton2.Checked ? TextBox1.Text : "noprice";
            SqlCommand _cmd = new SqlCommand("insertproduct2", _cn);
            _cmd.CommandType = CommandType.StoredProcedure;
            _cn.Open();

            _cmd.Parameters.AddWithValue("@Name", txtname.Text);
            _cmd.Parameters.AddWithValue("@Model", txtmodel.Text);
            _cmd.Parameters.AddWithValue("@Description", CKEditorControl1.Text);
            _cmd.Parameters.AddWithValue("@Price", price);

            _cmd.Parameters.AddWithValue("@Classification", DDL1.SelectedItem.Text);
            _cmd.Parameters.AddWithValue("@subset", DDL2.SelectedItem.Text);
            _cmd.Parameters.AddWithValue("@behcode", data);
            _cmd.Parameters.AddWithValue("@id",Convert.ToInt32(ViewState["Id"]));  
  int ID = Convert.ToInt32(_cmd.ExecuteScalar());
    if(ID>0)
{
       ViewState["Id"]= ID.ToString(); 
}


    

            _cn.Close();

            Response.Redirect(Request.Url.AbsoluteUri);


        
    }

  this.ClientScript.RegisterStartupScript(GetType(), "Javascript", "<script>alert('Updated Successfully')</script>");

Paste the above code in last in the button click event.