[ADDITION] Added databinding to the chatbox function.

Tried to broadcast the message, doesn't work yet.

Client/ViewModels/ViewModelGame.cs

@@ -1,10 +1,69 @@
-using System.Collections.ObjectModel;
+using GalaSoft.MvvmLight.Command;
+using SharedClientServer;
+using System.Collections.ObjectModel;
 using System.ComponentModel;
+using System.Diagnostics;
+using System.Windows.Input;
 
 namespace Client.ViewModels
 {
     class ViewModelGame : INotifyPropertyChanged
     {
+        ClientData data = ClientData.Instance;
         public event PropertyChangedEventHandler PropertyChanged;
+        public ObservableCollection<string> Messages { get; } = new ObservableCollection<string>();
+
+        private dynamic _payload;
+
+        private string _username;
+
+        private string _message;
+        public string Message
+        {
+            get
+            {
+                return _message;
+            }
+            set
+            {
+                _message = value;
+            }
+        }
+        public ICommand OnKeyDown { get; set; }
+
+        public ViewModelGame()
+        {
+            if (_payload == null)
+            {
+                _message = "";
+            }
+            else
+            {
+                _message = _payload.message;
+                _username = _payload.username;
+            }
+            OnKeyDown = new RelayCommand(ChatBox_KeyDown);
+        }
+
+        private void ChatBox_KeyDown()
+        {
+            //if enter then clear textbox and send message.
+            if (Message != string.Empty) AddMessage(Message);
+            Message = string.Empty;
+        }
+
+        internal void AddMessage(string message)
+        {
+            Messages.Add($"{data.User.Username}: {message}");
+
+            _payload = new
+            {
+                username = data.User.Username,
+                message = message
+            };
+
+            //Broadcast the message after adding it to the list!
+            data.Client.SendMessage(JSONConvert.GetMessageToSend(JSONConvert.MESSAGE, _payload));
+        }
     }
 }