Chat Application

Question

Please I need help

I am creating a chat application in ASP.NET C#. I used the step by Altaf Ansari on Signal R Chat App with Webform and Bootstrap - Part One.

I used the code in the chatHub Class by the code display error in the following

1. Context

2. Clients

3. OnDisconnected

 

The complete code is displayed below

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.AspNet.SignalR;

namespace CHAPP_WEB
{
    public class ChutHub
    {
        static List ConnectedUsers = new List();
        static List CurrentMessage = new List();
        ConnClass ConnC = new ConnClass();

        public void Connect(string userName)
        {
            var id = Context.ConnectionId;

            if (ConnectedUsers.Count(x => x.ConnectionId == id) == 0)
            {
                string UserImg = GetUserImage(userName);
                string logintime = DateTime.Now.ToString();
                ConnectedUsers.Add(new Users { ConnectionId = id, UserName = userName, UserImage = UserImg, LoginTime = logintime });

                // send to caller
                Clients.Caller.onConnected(id, userName, ConnectedUsers, CurrentMessage);

                // send to all except caller client
                Clients.AllExcept(id).onNewUserConnected(id, userName, UserImg, logintime);
            }
        }

        public void SendMessageToAll(string userName, string message, string time)
        {
            string UserImg = GetUserImage(userName);
            // store last 100 messages in cache
            AddMessageinCache(userName, message, time, UserImg);

            // Broad cast message
            Clients.All.messageReceived(userName, message, time, UserImg);
        }

        private void AddMessageinCache(string userName, string message, string time, string UserImg)
        {
            CurrentMessage.Add(new Messages { UserName = userName, Message = message, Time = time, UserImage = UserImg });

            if (CurrentMessage.Count > 100)
                CurrentMessage.RemoveAt(0);

            // Refresh();
        }

        public string GetUserImage(string username)
        {
            string RetimgName = "images/dummy.png";
            try
            {
                string query = "select Photo from tbl_Users where UserName='" + username + "'";
                string ImageName = ConnC.GetColumnVal(query, "Photo");

                if (ImageName != "")
                    RetimgName = "images/DP/" + ImageName;
            }
            catch (Exception ex)
            { }
            return RetimgName;
        }

        public override System.Threading.Tasks.Task OnDisconnected(bool stopCalled)
        {
            var item = ConnectedUsers.FirstOrDefault(x => x.ConnectionId == Context.ConnectionId);
            if (item != null)
            {
                ConnectedUsers.Remove(item);
                var id = Context.ConnectionId;
                Clients.All.onUserDisconnected(id, item.UserName);
            }
            return base.OnDisconnected(stopCalled);
        }
    }
}

Please help me out.

Thanks