Xamarin and Signal R - Chat Cross Platform

Using SignalR v2.x

2 parts:
Part 1: Create the core project, an MVC project, as a website in IIS.
Part 2: Xamarin and SignalR - Chat Cross Platform.


Part 2: Xamarin and SignalR

Common Issue:
Example:
SignalR - version of the client that isn't compatible with the server. Client version 1.4, server version undefined.

Error message: You are using a version of the client that isn't compatible  with the server.

This can be resolved easily by installing the same version from NuGet.


Sample - using SignalR Group.  - Chat.cshtml:
//https://code.msdn.microsoft.com/Getting-Started-with-c366b2f3
@{
    ViewBag.Title = "Chat";
}
<h2>Chat</h2>
<div class="container">
        <div id="typingstatus"></div>   
    <input type="text" id="message" />
    <input type="button" id="sendmessage" value="Send to everyone" />
        <input type="button" id="sendmessageToPeopleInRoom" value="Send to ppl in the same room" />
    <input type="hidden" id="displayname" />
        <input type="hidden" id="roomname" />
    <ul id="discussion"></ul>
</div>
@section scripts {
    <!--Script references. -->
    <!--The jQuery library is required and is referenced by default in _Layout.cshtml. -->
    <!--Reference the SignalR library. -->
    <script src="~/Scripts/jquery.signalR-2.2.0.min.js"></script>
    <!--Reference the autogenerated SignalR hub script. -->
    <script src="~/signalr/hubs"></script>
    <!--SignalR script to update the chat page and send messages.-->
    <script>
        $(function () {
            // Reference the auto-generated proxy for the hub.addNewMessageToPage
                var chat = $.connection.chatHub;



            // Create a function that the hub can call back to display messages.
                    //---------------Subscribe to when client is Typing and post a message to public
                chat.client.addNewMessageToPage = function (name, message) {

                    if (name == "typing") {
                        $('#typingstatus').html(message);
                    }else{
                // Add the message to the page.
                $('#discussion').append('<li><strong>' + htmlEncode(name)
                    + '</strong>: ' + htmlEncode(message) + '</li>');
                    }

                    //Clear the typing status
                    setTimeout("$('#typingstatus').empty();", 2000);
                };




            //---------------Subscribe to when client is Typing and post a message to private room
                chat.client.addChatMessage = function (name, message) {
                    $('#discussion').append('<li><strong>' + htmlEncode(name)
                    + '</strong>: ' + htmlEncode(message) + '</li>');
                };



            //--------------Subscribe to Client Join ROOM event
            chat.client.AddAnnouncement = function (roomName, message) {
                // Add the message to the page.
                $('#discussion').append('<li><strong><i>' + htmlEncode(message)
                                    + '</strong></i></li>');
            };


            //--------------General stuff
            // Get the user name and store it to prepend to messages.
            $('#displayname').val(prompt('Enter your name:', ''));
            $('#roomname').val(prompt('Enter the room name:', ''));

            // Set initial focus to message input box.
            $('#message').focus();


            $username = $('#displayname').val();
            $roomname = $('#roomname').val();

          //-------------Start the connection.
            $.connection.hub.start().done(function () {

                chat.server.joinRoom($username, $roomname);
               
                $('#sendmessage').click(function () {
                    // Call the Send to all client method on the hub.
                        chat.server.sendToAllClient($('#displayname').val(), $('#message').val());

                    // Clear text box and reset focus for next comment.
                    $('#message').val('').focus();
                });


                $('#sendmessageToPeopleInRoom').click(function () {
                    // Call the Send to all client method on the hub.
                    chat.server.sendToSpecificRoom($('#displayname').val(), $('#message').val(), $('#roomname').val());

                    // Clear text box and reset focus for next comment.
                    $('#message').val('').focus();
                });
               
            });
        });
        // This optional function html-encodes messages for display in the page.
        function htmlEncode(value) {
            var encodedValue = $('<div />').text(value).html();
            return encodedValue;
        }
    </script>
}
--------------------------------------------------------

Example of HUB: ChatHub.cs


using System;
using System.Web;
using Microsoft.AspNet.SignalR;
using System.Threading.Tasks;

namespace SignalRChat
{
    public class ChatHub : Hub
    {
        #region general method. Either individual to everyone. or broadcast.

        //In chat.chtml, the callback method is actually the client method name instead of method name. e.g: broadcastMessage
        public void SendToAllClient(string name, string message)
        {
            // Call the addNewMessageToPage method to update clients.
            Clients.All.addNewMessageToPage(name, message);

            Clients.All.broadcastMessage(name, message);
        }

        public void SendToSpecificRoom(string name, string message, string roomName)
        {
            Clients.Group(roomName).addChatMessage(name, message);
        }
        #endregion



        #region with the concept of using GROUP or ROOM
        //In javascript, need to turn the first letter of a method name to small cap.
        public void JoinRoom(string username, string roomName)
        {
            Groups.Add(Context.ConnectionId, roomName);
            RoomBroadcast(username + " has joined into " + roomName, roomName);
        }

        public void LeaveRoom(string roomName)
        {
            Groups.Remove(Context.ConnectionId, roomName);
        }

        //In chat.chtml, the callback method is actually the client method name instead of method name. e.g: broadcastMessage
        public void RoomBroadcast(string message, string roomName)
        {
            Clients.Group(roomName).AddAnnouncement(roomName, message);
        }


       
        #endregion


        public void Typing(string username, string message)
        {
            if (!string.IsNullOrEmpty(message)) {
                Clients.All.addNewMessageToPage("typing", username + " is typing: " + message);
            }
            else
            {
                Clients.All.addNewMessageToPage("typing", "");
            }
        }
    }
}