How to create a chat application in asp.net?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.SessionState;

namespace AJAXORama
{
  public class Global : System.Web.HttpApplication
{
  protected void Application_Start(object sender, EventArgs e)
  {
    // Code that runs on application startup
    List<string> messages = new List<string>();
    HttpContext.Current.Cache["Messages"] = messages;
  }
  // other generated code is here...
}


}
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
 
 
public partial class GroupChat : System.Web.UI.Page 
{ 
    protected void Page_Load(object sender, EventArgs e) 
    { 
    } 
 
    protected string GetUserID() 
    { 
        string strUserID =  
          (string) Session["UserID"]; 
        return strUserID; 
    } 
}

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
 
 
public partial class GroupChat : System.Web.UI.Page 
{ 
    protected void Page_Load(object sender, EventArgs e) 
    { 
    } 
    // other code goes here... 
    void ManageUI() 
    { 
        if (GetUserID() == null) 
 
        { 
            // if this is the first request, then get the user’s ID 
            TextBoxMessage.Enabled = false; 
            TextBoxConversation.Enabled = false; 
            ButtonAddYourMessage.Enabled = false; 
 
            ButtonSubmitID.Enabled = true; 
            TextBoxUserID.Enabled = true; 
        } 
        else 
        { 
            // if this is the first request, then get the user’s ID 
            TextBoxMessage.Enabled = true; 
            TextBoxConversation.Enabled = true; 
            ButtonAddYourMessage.Enabled = true; 
 
            ButtonSubmitID.Enabled = false; 
            TextBoxUserID.Enabled = false; 
        } 
    } 
}
  
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 494  Part V  Dynamic Data, XBAP, MVC, AJAX, and Silverlight
using System.Web.UI; 
using System.Web.UI.WebControls; 
 
public partial class GroupChat : System.Web.UI.Page 
{ 
    protected void Page_Load(object sender, EventArgs e) 
    { 
    } 
   // other page code goes here... 
    protected void ButtonSubmitID_Click(object sender, EventArgs e) 
    { 
        Session["UserID"] = TextBoxUserID.Text; 
        ManageUI(); 
    } 
}
  
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
 
public partial class GroupChat : System.Web.UI.Page 
{ 
   // other page code goes here... 
    void RefreshConversation() 
    { 
        List<string> messages = (List<string>)Cache["Messages"]; 
        if (messages != null) 
        { 
            string strConversation = ""; 
 
            int nMessages = messages.Count; 
 
            for(int i = nMessages-1; i >=0; i--) 
            { 
                string s; 
 
                s = messages[i]; 
                strConversation += s; 
                strConversation += "\r\n"; 
            } 
 
            TextBoxConversation.Text =  
                strConversation; 
        } 
    } 
} 
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
 
public partial class GroupChat : System.Web.UI.Page 
{ 
    // Other code goes here... 
    protected void ButtonAddYourMessage_Click(object sender,  
                                               EventArgs e) 
    { 
        // Add the message to the conversation... 
        if (this.TextBoxMessage.Text.Length > 0) 
        { 
            List<string> messages = (List<string>)Cache["Messages"]; 
            if (messages != null) 
            { 
                TextBoxConversation.Text = ""; 
 
                string strUserID = GetUserID(); 
 
                if (strUserID != null) 
                { 
                    messages.Add(strUserID +  
                        ": " +  
                        TextBoxMessage.Text); 
                    RefreshConversation(); 
                    TextBoxMessage.Text = ""; 
                } 
            } 
        } 
    } 
}
  
using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Web; 
using System.Web.UI; 
using System.Web.UI.WebControls; 
 
using System.Xml.Linq; 
using System.Collections.Generic; 
 
public partial class GroupChat : System.Web.UI.Page 
{ 
    // Other code goes here... 
    protected void Page_Load(object sender, EventArgs e) 
    { 
        ManageUI(); 
        RefreshConversation(); 
    } 
}</string></string></string></string>