Update textbox on client on callback from server in wcf

[manugm_1987]

Hello everyone

I am creating a simple chat application using wcf. The problem is on callback i am not able to display the message on to client rich text box. i.e when the user clicks on whisper button the server makes a callback to client the callback is successfull, but the message sent wont be updated in the client rich text box. Please help

I am using two winforms for client and server and one common interface

The interface code is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
 
namespace InterfaceLibrary
{
    [ServiceContract(CallbackContract = typeof(IChatCallback), SessionMode = SessionMode.Required)]
    public interface IChat
    {
        [OperationContract]
        void JoinChat(string username);
 
        [OperationContract]
        void SendMessage(string sender, string message);
 
        [OperationContract]
        void LeaveChat(string username);
 
        //[OperationContract]
        //string[] GetOnlineUsers();
    }
 
    public interface IChatCallback
    {
        [OperationContract(IsOneWay=true)]
        void ReceiveMessage(string from, string message);
 
        [OperationContract(IsOneWay = true)]
        void UserEnter(string name);
 
        [OperationContract(IsOneWay = true)]
        void UserLeave(string name);
    }
}

The server code is

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
using InterfaceLibrary;
using System.Windows.Forms;
using ChatClient;
 
namespace WCFChat
{
    [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall,ConcurrencyMode=ConcurrencyMode.Reentrant)]
    class ChatServer:IChat
    {
        //public delegate void ReceiveMsg(string sender, string message);
        //public event ReceiveMsg Receivemessage;

        IChatCallback callback = null;
        Client cs = new Client();
        public static Dictionary<string,> ListofUsers = new Dictionary<string,>();
        public void JoinChat(string username)
        {
            callback = OperationContext.Current.GetCallbackChannel<ichatcallback>();
            if (CheckUserExists(username) == true)
            {
                ListofUsers.Add(username, callback);
                
            }
            else
            {
                MessageBox.Show("Username already exixts!: Please select different Name");
            }
            ListofUsers.ToArray();
            
        }
 
        public void SendMessage(string sender, string message)
        {
            foreach (string str in ListofUsers.Keys)
            {
                //i have hardcoded the username to abc to just check. So when user
                //logs in in has abc this portion will be executed and makes call 
                //to ReceiveMessage of client where the textbox needs to be updated
                //with the message sent. But in my case textbox is not updated.
                if (str == "abc")
                {
                    IChatCallback icall = ListofUsers[str];
                    icall.ReceiveMessage(sender,message);
                    //Receivemessage += new ReceiveMsg(icall.ReceiveMessage);
                    //Receivemessage(sender, message);
                    
                }
            }
        }
 
        public void LeaveChat(string name)
        {
        }
 
        //public string[] GetOnlineUsers()
        //{
        //    return ;
        //}

        public bool CheckUserExists(string username)
        {
            foreach (string name in ListofUsers.Keys)
            {
                if(username.Equals(name,StringComparison.OrdinalIgnoreCase))
                     return false;
            }
            return true;
        }
    }
}

This above server code is in a separate class file and i host the server using another winform which is under the same project.No problem with server hosting and clients connecting to the server.So i am skipping those parts.

The client which code is

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.ServiceModel;
using InterfaceLibrary;
using System.Diagnostics;
using System.Threading;
 
namespace ChatClient
{
    [CallbackBehavior(UseSynchronizationContext = false)]
    public partial class Client : Form,IChatCallback
    {
        public delegate void ReceiveMsg(string sender, string message);
        public event ReceiveMsg Receivemessage;
 
        IChat chatter = null;
        DuplexChannelFactory<ichat> connect;
        InstanceContext instanceContext = null;
 
        
        public string CurrentUser;
        public Client()
        {
            InitializeComponent();
            
        }
 
        private void login_btn_Click(object sender, EventArgs e)
        {
            //CallBackHandler instance = new CallBackHandler();
            //instanceContext = new InstanceContext(new CallBackHandler());
            Client instance = new Client();
            instanceContext = new InstanceContext(new Client());
          
            connect = new DuplexChannelFactory<ichat>(instanceContext, "TcpBinding");
            chatter = connect.CreateChannel();
            
            if (!string.IsNullOrEmpty(login_txt.Text))
            {
                CurrentUser = login_txt.Text;
                chatter.JoinChat(CurrentUser);
               
            }
            else
            {
                MessageBox.Show("Please Enter Valid UserName", "WARNING", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            }
        }
        
 
        //When user clicks on whisper button it goes to server sendmessage method
        //Where callback is implemented
        private void whispher_btn_Click(object sender, EventArgs e)
        {
            chatter.SendMessage(login_txt.Text, rtxt_message.Text);
            
        }
 

 
        #region IChatCallback Members
        //the callback calls this method, but the rich textbox wont be updated 

        public void ReceiveMessage(string from, string message)
        {
            rtxt_message.AppendText(from+":"+message);
            
        }
 
        public void UserEnter(string name)
        {
            throw new NotImplementedException();
        }
 
        public void UserLeave(string name)
        {
            throw new NotImplementedException();
        }
 
        #endregion
    }
}

How to update the richtext box of the client with the message sent.Please help

Thank you