Creation of Chat Box in C#

Creation of 'Chat Box' in C#

using System;

using System.Collections.Generic;
using System.Linq;
// you have to add these namespaces for creation and for web control
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls; 

public partial class Default3 : System.Web.UI.Page

{
    protected void Page_Load(object sender, EventArgs e)
    {
        // its on you 

    }     

    protected void Button1_Click(object sender, EventArgs e)
    {

        Window1.Visible = true;
    }
    private string Chat
    {
        get
        {
            if (Application["a"] == null)
                Application["a"] = "";
            return Application["a"].ToString();
        } 

        set

        {
            Application["a"] = value;
        }
    } 

    protected void Timer1_Tick(object sender, EventArgs e)

    {
        Label1.Text = Chat;
    }

     protected void Button2_Click(object sender, EventArgs e)
    {

        Chat = TextBox1.Text + "<br/>" + Chat;
    }
}