AJAX Simple Chat

spilafis

2.67/5 (7 votes)

24 Nov 2006CPOL1 min read

1.1K

A simple AJAX and C# .NET chat. Light-weight, and doesn’t require any applet or server!

Download source files - 50.9 KB

Introduction

This is a simple AJAX based chat done in C#.

Instructions

Important note: This is a chat made for ASP.NET 2.0 (VS2005 or later).

Add a new web form to your solution, name it ChatPage.aspx, choose C# language.
Copy and paste the page HTML to the source view of your web form.
Copy and paste the page code-behind to the code-behind file of your web form named ChatPage.aspx.cs.
Copy and paste the Business logic to a new class in your App_Code folder named SPilafisChatLogic.cs.
Add AJAX for ASP.NET 2.0 (VS2005) to your solution. (With VS2005, you just have to drag and drop the DLL in your bin folder and add a couple of lines to your web.config.)
Get some french fries and enjoy!

Page HTML

ASP.NET

<%@ Page Language="C#" AutoEventWireup="true" 
   CodeFile="ChatPage.aspx.cs" Inherits="ChatPage" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" >
<head id="Head1" runat="server">
    <title>Chat Ajax .NET</title>
    <style type="text/css">
    td {
        font-family: Arial;
        font-size: 8pt;
       }
    </style>
    <!--
    License and Disclaimer: All the intructions, code, html and everything 
    presented with this solution is provided 'as is' with no warranties what so ever.
    The only condition for you to use this software is that you keep the link 
    to http://www.spilafis.com.ar in the chat page as provided. 
    Please support freeware keeping the link and clicking on my sponsors.
    Thank you!
    !-->
</head>
<body>
    <form id="form1" runat="server" onsubmit="return false;">
<br />
<br />
<br />
<br />
<br />
<br />
<br />
    <table align="center" width="732" 
        border="0" cellpadding="0" cellspacing="0">
    <tr>
        <td>
        <textarea id="txtChatFrame" runat="server" 
           rows="15" 
           style="width:527px; border:1px solid #aaaaaa; padding:4px;" 
           readonly="readonly"></textarea><br/>
        </td>
        <td valign="top">
            <div style="overflow: auto; height: 226px; border-top: 
                           solid 2px gray; border-bottom: solid 2px gray; 
                           border-right: solid 1px gray; border-left: solid 1px gray; ">
                <asp:GridView ID="grvUsers" runat="server" 
                    AutoGenerateColumns="False" BackColor="White"
                    BorderColor="#DEDFDE" BorderStyle="None" 
                    BorderWidth="1px" CellPadding="1" 
                    ForeColor="Black"
                    GridLines="Vertical" Height="30px">
                    <FooterStyle BackColor="#CCCC99" />
                    <Columns>
                        <asp:BoundField HeaderText="User" 
                          ReadOnly="True" DataField="ChatUsers">
                            <ItemStyle Width="110px" />
                            <HeaderStyle Height="10px" />
                        </asp:BoundField>
                        <asp:BoundField HeaderText="Last Activity" 
                                  DataField="ChatLastActivity">
                            <ItemStyle Width="190px" />
                            <HeaderStyle Height="10px" />
                        </asp:BoundField>
                    </Columns>
                    <RowStyle BackColor="#F7F7DE" />
                    <SelectedRowStyle BackColor="#CE5D5A" 
                      Font-Bold="True" ForeColor="White" />
                    <PagerStyle BackColor="#F7F7DE" 
                      ForeColor="Black" HorizontalAlign="Right" />
                    <HeaderStyle BackColor="#6B696B" 
                      Font-Bold="True" ForeColor="White" />
                    <AlternatingRowStyle BackColor="White" />
                </asp:GridView>
            </div>
            <input id="btnRefresh" runat="server" 
              type="submit" onclick="document.forms['form1'].submit();" 
              value="Refresh" 
              style="cursor:pointer;border:1px solid gray; height: 15px; 
                     width: 100%; font-size: 7pt;" 
              size="20"/>
            </td>            
    </tr>
    <tr>
        <td>
        
        <table border="0" cellpadding="0" 
            cellspacing="5" style="width:527px;">
        <tr>
            <td align="right" valign="middle">Message: </td>
            <td align="left" style="height: 45px" valign="top">
                <table border="0" cellpadding="0" cellspacing="2">
                <tr>
                    <td><textarea cols="70" rows="2" 
                      id="txtMssg" 
                      style="border:1px solid gray; width: 370px; height: 37px;" 
                      onkeyup="SendByKey(event.keyCode);"></textarea></td>
                    <td><input id="btnSend" type="button" 
                      value="Send" onclick="Send()" 
                      style="cursor:pointer;border:1px solid gray; 
                            height: 42px;"/></td>
                </tr>
                </table></td>  
        </tr>
        <tr>
            <td align="right" valign="middle" 
               style="width:70px">User Name: </td>
            <td align="left">
                <table border="0" 
                    cellpadding="0" cellspacing="2">
                <tr>
                    <td><input id="txtName" type="text" 
                       maxlength="10" 
                       style="border:1px solid #aaaaaa; width: 145px;" 
                       onblur="ChangeUserName(this);"/ 
                       value="<%=SpilafisChatLogic.Chat.GetUserName()%>" />
                    </td>
                    <td>
                       Get source code!: 
                       <a href="http://www.spilafis.com.ar">
                                http://www.spilafis.com.ar</a>
                    </td>
                </tr>
                </table>
            </td>  
        </tr>
        </table>

        </td>
        <td valign="middle">
            <br />
            <table border="0" cellpadding="0" cellspacing="0">
                <tr>
                    <td align="center">Users Writing: <br />
                      (max. <%=SpilafisChatLogic.Chat.MaxLoggedInUsers.ToString()%>)
                    </td>
                    <td align="right"><span id="spnW">0</span> <br /><br /></td>
                </tr>
                <tr>
                    <td colspan="2"> <br /></td>
                </tr>
                <tr>
                    <td align="left">Users Reading:    </td>
                    <td align="right"><span id="spnR">0</span></td>
                </tr>
            </table>
        </td>
    </tr>
    </table>
    <br />
    <br />

<script type="text/javascript" language="javascript">

function ChangeUserName(otxtName)
{
    var tentative_name = otxtName.value;
    if(tentative_name=="")
        alert("You must enter a user name to be able to chat.");
    else
    {
        if(tentative_name!=last_user_name)
        {
            var otxtMssg = document.getElementById("txtMssg");
            var obtnSend = document.getElementById("btnSend");

            var ret = Chat.ChangeUserName(tentative_name);
            if(ret!=null && ret.error!=null && ret.error!="")
            {
                otxtName.value = last_user_name;
                alert(new String(ret.error).replace("System.Exception ",""));
            }
            else
            {
                last_user_name = otxtName.value;
                obtnSend.disabled = false;
                otxtMssg.disabled = false;
                otxtMssg.focus();
            }
        }
    }
}

function Send()
{
    var otxtName = document.getElementById("txtName");
    if(otxtName.value!="")
    {
        var otxtMssg = document.getElementById("txtMssg");
        if(!otxtMssg.disabled)
        {
            var ret = Chat.Post(otxtMssg.value);
            if(ret!=null && ret.error!=null)
            {
                alert(new String(ret.error).replace("System.Exception ",""));
            }
            otxtMssg.value = "";
            otxtMssg.focus();
        }
    }
    else
    {
        if(!otxtName.disabled)
        {
            alert("Enter a user name");
            otxtName.focus();
        }
    }
}

function SendByKey(keycode)
{
    if (keycode == 13)
        Send();
    event.returnValue = false;
}

var cycles = 20;
var add_wait_cycles = 20;
var reload_wait = 700;
var last_user_name = "";
var max_chat_lines = <%=SpilafisChatLogic.Chat.MaxChatLines%>;
function Reload()
{
    var ret;
    cycles++;;
    if(cycles>=add_wait_cycles)
    {
        cycles = 0;

        // Get users writing
        ret = Chat.GetUsersWriting();
        if(ret!=null && (ret.error==null || ret.error=="") && 
                  ret.value!=null && ret.value!="")
            document.getElementById("spnW").innerHTML = ret.value;

        // Get users reading
        ret = Chat.GetUsersReading();
        if(ret!=null && (ret.error==null || ret.error=="") && 
                   ret.value!=null && ret.value!="")
            document.getElementById("spnR").innerHTML = ret.value;
    }

    // If not logged in to write then try to logg in the user
    var otxtMssg = document.getElementById("txtMssg");
    if(otxtMssg.disabled)
    {
        var otxtName = document.getElementById("txtName");
        if(otxtName.value=="")
        {
            ret = Chat.GetNextUserName();
            if(ret!=null && ret.error==null && 
                     ret.value!=null && ret.value!="")
            {
                    otxtName.value = ret.value;
                    LoggedIn();
                    alert("You have been logged in");
            }
        }
        else
        {
            last_user_name = otxtName.value;
            otxtMssg.disabled = false;
            var obtnSend = document.getElementById("obtnSend");
            obtnSend.disabled = false;
            otxtMssg.focus();
        }
    }

    // Read Chat
    var ret = Chat.Read();
    if(ret!=null && ret.error!=null)
    {
        alert("A critical error ocurred: " + new String(ret.error).replace(
          "System.Exception ","") + 
          "\nPlease reload page to try again.");
        return;
    }
    var value = ret.value;
    if(value!=null && value!="")
    {
        var otxtChatFrame = 
          document.getElementById("<%=txtChatFrame.ClientID%>");
        var already_read = otxtChatFrame.value;
        //var all = value + already_read;
        var all = already_read + value;
        if(all!="")
        {
            var arr = all.split("\n");
            if(arr.length>max_chat_lines)
            {
                all = "";
                //for(var i=0; i<max_chat_lines; i++)
                for(var i=(arr.length-max_chat_lines); i<arr.length; i++)
                    all += arr[i] + "\n";
            }
        }    
        otxtChatFrame.value = all;
        // Scroll down to the last read line
        otxtChatFrame.scrollTop=otxtChatFrame.scrollHeight;
    }

    window.setTimeout("Reload();", reload_wait);
}

function Start()
{
    Reload();

    // Initial scroll down to the last read line (in case Refresh is hit)
    var otxtChatFrame = document.getElementById("<%=txtChatFrame.ClientID%>");
    otxtChatFrame.scrollTop=otxtChatFrame.scrollHeight;
}

function LoggedIn()
{
    var otxtName = document.getElementById("txtName");
    var obtnSend = document.getElementById("btnSend");
    var otxtMssg = document.getElementById("txtMssg");
    last_user_name = otxtName.value;
    otxtName.disabled = false;
    obtnSend.disabled = false;
    otxtMssg.disabled = false;
    otxtMssg.focus();
}

// Call to start!
Start();
</script>
</form>
</body>
</html>

Page code-behind

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Threading;
using System.Globalization;

/// <summary>
/// License and Disclaimer: All the intructions, code, html 
/// and everything presented with this solution
/// is provided 'as is' with no warranties what so ever.
/// The only condition for you to use this software is that
/// you keep the link to http://www.spilafis.com.ar in the chat page
/// as provided. Please support freeware keeping the link and clicking on my sponsors.
/// Thank you!
/// </summary>
public partial class ChatPage : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // Register AJAX
        Ajax.Utility.RegisterTypeForAjax(typeof(SpilafisChatLogic.Chat));
        
        UpdateUsersGridView();
    }

    public void UpdateUsersGridView()
    {
        // Update grid
        grvUsers.DataSource = SpilafisChatLogic.Chat.GetUsersDataSource();
        grvUsers.DataBind();
    }
    protected void btnRefresh_ServerClick(object sender, EventArgs e)
    {
        UpdateUsersGridView();
    }
}

Business logic

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Threading;
using System.Globalization;

namespace SpilafisChatLogic
{
    /// <summary>
    /// License and Disclaimer: All the intructions, code, html
    /// and everything presented with this solution
    /// is provided 'as is' with no warranties what so ever.
    /// The only condition for you to use this software is that you keep
    /// the link to http://www.spilafis.com.ar in the chat page as provided.
    /// Please support freeware keeping the link and clicking on my sponsors.
    /// Thank you!
    /// </summary>
    public class Business
    {
        public Business()
        {
        }

        public static User CurrentUser
        {
            get
            {
                if (HttpContext.Current.Session["ChatCurrentUser"] == null)
                    HttpContext.Current.Session["ChatCurrentUser"] = new User();

                return (User)HttpContext.Current.Session["ChatCurrentUser"];
            }
            set
            {
                HttpContext.Current.Session["ChatCurrentUser"] = value;
            }
        }

        public static App CurrentApp
        {
            get
            {
                if (HttpContext.Current.Application["ChatCurrentApp"] == null)
                    HttpContext.Current.Application["ChatCurrentApp"] = new App();

                return (App)HttpContext.Current.Application["ChatCurrentApp"];
            }
            set
            {
                HttpContext.Current.Application["ChatCurrentApp"] = value;
            }
        }
    }

    public class User
    {
        #region Private Members

        private bool m_ajax_chat_counted;
        private string m_ajax_chat_user_name;
        private int m_ajax_chat_last_read_id;

        private bool m_code_access_enabled;

        #endregion

        public User()
        {
            m_ajax_chat_counted = false;
            m_ajax_chat_user_name = "";
            m_ajax_chat_last_read_id = -1;

            m_code_access_enabled = false;
        }

        #region Properties

        public bool AjaxChatCounted
        {
            get { return m_ajax_chat_counted; }
            set { m_ajax_chat_counted = value; }
        }

        public string AjaxChatUserName
        {
            get { return m_ajax_chat_user_name; }
            set { m_ajax_chat_user_name = value; }
        }

        public int AjaxChatLastReadId
        {
            get { return m_ajax_chat_last_read_id; }
            set { m_ajax_chat_last_read_id = value; }
        }

        #endregion

    }


    public class App
    {
        #region Private Members

        private int m_ajax_chat_users_r;
        private Hashtable m_ajax_chat_users_w;
        private Hashtable m_ajax_chat_users_w_last_activity;
        private ArrayList m_ajax_chat;

        #endregion


        public App()
        {
            m_ajax_chat_users_w = new Hashtable();
            m_ajax_chat_users_w_last_activity = new Hashtable();
            m_ajax_chat = new ArrayList();
        }


        #region Properties

        public int AjaxChatUsersR
        {
            get { return m_ajax_chat_users_r; }
            set { m_ajax_chat_users_r = value; }
        }

        public Hashtable AjaxChatUsersW
        {
            get { return m_ajax_chat_users_w; }
            set { m_ajax_chat_users_w = value; }
        }

        public Hashtable AjaxChatUsersWLastActivity
        {
            get { return m_ajax_chat_users_w_last_activity; }
            set { m_ajax_chat_users_w_last_activity = value; }
        }

        public ArrayList AjaxChat
        {
            get { return m_ajax_chat; }
            set { m_ajax_chat = value; }
        }

        #endregion
    }


    public class Chat
    {
        #region Constants

        public static int MaxMessageLength = 100;
        public static int MaxChatLines = 50;
        public static int MaxLoggedInUsers = 5;
        public static string[] BadWords = { "a**hole", 
               "boludo"}; // Add your bad word dictionary here

        #endregion

        public Chat()
        {
        }

        #region Methods

        private static void IncrementUsersReading()
        {
            Business.CurrentApp.AjaxChatUsersR = GetIntUsersReading() + 1;
        }

        private static int GetIntUsersReading()
        {
            return Business.CurrentApp.AjaxChatUsersR;
        }

        private static int GetId(string message)
        {
            return Convert.ToInt32(message.Split('-')[0]);
        }

        private static string GetMessage(string message)
        {
            return message.Split('-')[1];
        }

        private static string GetNextId(ArrayList ajax_chat_list)
        {
            int id = GetMaxId(ajax_chat_list);
            if (id < Int32.MaxValue)
                id++;
            else
                id = 0;
            return id.ToString() + "-";
        }

        private static int GetMaxId(ArrayList ajax_chat_list)
        {
            if (ajax_chat_list.Count > 0)
                return GetId(ajax_chat_list[0].ToString());
            else
                return 0;
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static string GetUserName()
        {
            if (Business.CurrentUser.AjaxChatUserName == "")
                Chat.GetNextUserName();
            return Business.CurrentUser.AjaxChatUserName;
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static string GetNextUserName()
        {
            string user_name = "";
            // Count user reading if not counted yet
            if (!Business.CurrentUser.AjaxChatCounted)
            {
                Business.CurrentUser.AjaxChatCounted = true;
                IncrementUsersReading();  // Is decremented in session end
            }
            else
            {
                if (Business.CurrentUser.AjaxChatUserName != null && 
                          Business.CurrentUser.AjaxChatUserName != "")
                    return Business.CurrentUser.AjaxChatUserName;
            }

            int user_number = Business.CurrentApp.AjaxChatUsersW.Count + 1;
            // If user may log in 
            if (user_number <= MaxLoggedInUsers)
            {
                // Get first not used guest user name
                while (Business.CurrentApp.AjaxChatUsersW["ChatGuest" + 
                            user_number.ToString()] != null)
                {
                    if (user_number < int.MaxValue)
                        user_number++;
                    else
                        return "";
                }

                // Add to writing users list
                Business.CurrentApp.AjaxChatUsersW.Add("Guest" + 
                                    user_number.ToString(), 1);

                // Save user name to session
                Business.CurrentUser.AjaxChatUserName = 
                   "Guest" + user_number.ToString();

                UpdateUserLastActivityTime();
            }
            return user_name;
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static void ChangeUserName(string tentative_name)
        {
            if (Business.CurrentUser.AjaxChatUserName == "")
            {
                int user_number = Business.CurrentApp.AjaxChatUsersW.Count + 1;
                // If user may not log in inform
                if (user_number > MaxLoggedInUsers)
                    throw new Exception("Max. number of writing " + 
                       "users reached. You'll be inform when someone leaves.");
            }

            tentative_name = tentative_name.Trim();
            if (tentative_name == "")
                throw new Exception("You must enter a user name to be able to chat.");
            if (tentative_name.IndexOf('-') >= 0)
                throw new Exception("Character '-' is not allowed in the user name.");
            if (tentative_name.Length > 10)
                tentative_name = tentative_name.Substring(0, 10);

            // If exists inform
            if (Business.CurrentApp.AjaxChatUsersW[tentative_name] != null)
                throw new Exception("User name already in use. Please enter another.");

            // Remove old user name from the list
            // Add to writing users list
            ChangeUserNameInWList(tentative_name);

            // Save user name to session
            Business.CurrentUser.AjaxChatUserName = tentative_name;

            UpdateUserLastActivityTime();
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static void ChangeUserNameInWList(string new_name)
        {
            // If it already had a user name then remove from writing users
            if (Business.CurrentUser.AjaxChatUserName != null && 
                    Business.CurrentUser.AjaxChatUserName != "")
            {
                Business.CurrentApp.AjaxChatUsersW.Remove(
                           Business.CurrentUser.AjaxChatUserName);

                // If it had a saved last activity time remove it
                Business.CurrentApp.AjaxChatUsersWLastActivity.Remove(
                         Business.CurrentUser.AjaxChatUserName);

                // Add to writing users list
                Business.CurrentApp.AjaxChatUsersW.Add(new_name, 1);
                // NOTE: It is not necessary to add it to the last activity
                // table because it will be added after this
            }
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static void Post(string message)
        {
            // Cut max message length
            message = message.Trim();
            if (message.Length > MaxMessageLength)
                message = message.Substring(0, MaxMessageLength);

            if (message != "")
            {
                // Add time and nickname to identify message
                string message_head = 
                  Business.CurrentUser.AjaxChatUserName + " says: ";
                message = message_head + message;

                ValidateMessage(Business.CurrentApp.AjaxChat, message);

                // Add message id
                message = GetNextId(Business.CurrentApp.AjaxChat) + message;

                // Insert new message
                Business.CurrentApp.AjaxChat.Insert(0, message);

                // Delete lines after MaxChatLines
                while (Business.CurrentApp.AjaxChat.Count > MaxChatLines)
                    Business.CurrentApp.AjaxChat.RemoveAt(
                    Business.CurrentApp.AjaxChat.Count - 1);

                UpdateUserLastActivityTime();
            }
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static void ValidateMessage(ArrayList ajax_chat_list, string message)
        {
            int index;
            // Create array list of chat without message numbers
            ArrayList ajax_chat_nonumbers = new ArrayList();

            for (index = 0; index < ajax_chat_list.Count; index++)
                ajax_chat_nonumbers.Add(ajax_chat_list[index].ToString().Split('-')[1]);

            // Check for spam
            if (ajax_chat_nonumbers.Contains(message))
                throw new Exception("Please no spam...");

            // Create message words array
            string[] m_w = message.Replace("\n", " ").Replace("\r", "").Split(' ');
            ArrayList message_words = new ArrayList();
            for (index = 0; index < m_w.Length; index++)
                message_words.Add(m_w[index]);

            // Check for bad words
            for (index = 0; index < BadWords.Length; index++)
                if (message_words.Contains(BadWords[index]))
                    throw new Exception("Please no bad words...");
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static void UpdateUserLastActivityTime()
        {
            if (Business.CurrentUser.AjaxChatUserName != null && 
                       Business.CurrentUser.AjaxChatUserName != "")
              UpdateUserLastActivityTime(
                    Business.CurrentApp.AjaxChatUsersWLastActivity);
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static void UpdateUserLastActivityTime(
               Hashtable ajax_chat_users_w_last_activity)
        {
            if (ajax_chat_users_w_last_activity<Business.CurrentUser.AjaxChatUserName> 
                                                                                 == null)
                ajax_chat_users_w_last_activity.Add(
                     Business.CurrentUser.AjaxChatUserName, DateTime.Now);
            else
                ajax_chat_users_w_last_activity<
                   Business.CurrentUser.AjaxChatUserName> = DateTime.Now;
        }

        public static DataTable GetUsersDataSource()
        {
            // Create data source
            DataTable dtSource = new DataTable();
            dtSource.Columns.Add(new DataColumn("ChatUsers"));
            dtSource.Columns.Add(new DataColumn("ChatLastActivity"));
            DataRow drSource;
            DateTime last_activity;

            if (Business.CurrentApp.AjaxChatUsersW.Keys.Count > 0)
            {
                // Add list of users to datasource
                foreach (object key in Business.CurrentApp.AjaxChatUsersW.Keys)
                {
                    drSource = dtSource.NewRow();
                    drSource["ChatUsers"] = key.ToString();
                    // Get last activity time
                    if (Business.CurrentApp.AjaxChatUsersWLastActivity[key] != null)
                    {
                      last_activity = 
                        (DateTime)Business.CurrentApp.AjaxChatUsersWLastActivity[key];
                      // Convert to GMT time
                      Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
                      string dateFormat = 
                        CultureInfo.InvariantCulture.DateTimeFormat.RFC1123Pattern.Replace(
                        "'GMT'", "zzz");
                      string dateString = last_activity.ToString(dateFormat);
                      drSource["ChatLastActivity"] = dateString;
                    }
                    else
                        drSource["ChatLastActivity"] = "<none>";
                    dtSource.Rows.Add(drSource);
                }
            }
            else
            {
                drSource = dtSource.NewRow();
                drSource["ChatUsers"] = "<none>";
                drSource["ChatLastActivity"] = "<none>";
                dtSource.Rows.Add(drSource);
            }


            // Sort by user name
            dtSource.DefaultView.Sort = "ChatUsers";

            return dtSource;
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static string Read()
        {
            int id;
            int max_id = 0;
            string message;

            // Create chat list if not created
            System.Text.StringBuilder chat = new System.Text.StringBuilder();

            // Get chat from application level
            ArrayList ajax_chat_list = Business.CurrentApp.AjaxChat;

            // Get last read id from user session if already saved
            int last_read_id = Business.CurrentUser.AjaxChatLastReadId;

            // Write it to a string
            int index;
            ArrayList chat_arr = new ArrayList();
            for (index = 0; index < ajax_chat_list.Count; index++)
            {
                id = GetId(ajax_chat_list[index].ToString());
                if (index == 0)
                    max_id = id;
                message = GetMessage(ajax_chat_list[index].ToString());

                // If last read message read reached then stop reading
                if (id == last_read_id)
                    break;
                // Note: Why not "<="?
                //       Because "<=" may cause stop of reading
                // Example: If last message read is 9, and then the id 10 message was sent
                //          and then the id message 1 was sent,
                //          first message read would be id 1 that is < than 9
                //          and wouldn't be read although it should be
                //          (if read, comparing just equal,
                //           then id 10 would be read and in 9 it would stop)

                chat_arr.Add(System.Web.HttpUtility.HtmlEncode(message) + "\n");
                //chat.Append(Server.HtmlEncode(message) + "\n");
            }

            // Build inverted order chat string
            for (index = chat_arr.Count - 1; index >= 0; index--)
                chat.Append(chat_arr[index].ToString());

            // Set max_id as new last_read_id to user session
            Business.CurrentUser.AjaxChatLastReadId = max_id;

            UpdateUserLastActivityTime();

            // Return chat string to user with max_id to set as new last_read_id
            return chat.ToString();
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static string GetUsersWriting()
        {
            return Business.CurrentApp.AjaxChatUsersW.Count.ToString();
        }

        [Ajax.AjaxMethod(Ajax.HttpSessionStateRequirement.ReadWrite)]
        public static string GetUsersReading()
        {
            return GetIntUsersReading().ToString();
        }

        #endregion
    }
}

See a working example here: http://spilafis.com.ar/ChatPage.aspx.

Or a more complex (same code but enhanced) but better working example: http://spilafis.com.ar/ChatAjaxNet.aspx.

License and Disclaimer

All the instructions, code, HTML, and everything else presented in this page is provided 'as is' with no warranties what so ever. The only condition for you to use this software is that you keep the link to http://www.spilafis.com.ar in the chat page as provided. Please support freeware, keeping the link.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)