Simple Chat Page in ASP.NET using C#

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
namespace StructuredSites
{
 /// <summary>
 /// Summary description for chat.
 /// </summary>
 public class chat : System.Web.UI.Page
 {
  protected System.Web.UI.WebControls.TextBox txtChatBox;
  protected System.Web.UI.WebControls.TextBox txtMessage;
  protected System.Web.UI.WebControls.Button btnPost;
  protected System.Web.UI.WebControls.TextBox txtMyName;
  protected System.Web.UI.WebControls.Button btnClearLog;
 
  void Page_Load(object sender, System.EventArgs e)
  {
   txtChatBox.Text = "Welcome to SS Chat Online!";
  }

  public void btnClearLog_Click(object sender, EventArgs e)
  {
   Application["ChatLog"] = "";
   txtChatBox.Text = (string)Application["ChatLog"];
  }

  public void btnPost_Click(object Sender, EventArgs e)
  {
   string tab = "\t";
   string newline = "\r";
   string messageLog = (string)Application["ChatLog"];
   string newMessage = txtMyName.Text + ":" + txtMessage.Text + newline + messageLog;
   
   if (newMessage.Length > 500)
   {
    newMessage = newMessage.Substring(0,499);
   }

   Application["ChatLog"] = newMessage;

   txtChatBox.Text = (string)Application["ChatLog"];
  }

  #region Web Form Designer generated code
  override protected void OnInit(EventArgs e)
  {
   //
   // CODEGEN: This call is required by the ASP.NET Web Form Designer.
   //
   InitializeComponent();
   base.OnInit(e);
  }
  
  /// <summary>
  /// Required method for Designer support - do not modify
  /// the contents of this method with the code editor.
  /// </summary>
  private void InitializeComponent()
  {    
   this.btnPost.Click += new System.EventHandler(this.btnPost_Click);
   this.Load += new System.EventHandler(this.Page_Load);

  }
  #endregion

 }
}