Chat Server and WPF Client

Client

For the client code I used WPF and the MVVM pattern. From the bottom up the first thing I used is a DelegateCommand 

   1 using System;
   2 using System.Windows.Input;
   3 
   4 namespace ChatClient
   5 {
   6     class DelegateCommand : ICommand
   7     {
   8         private readonly Predicate<object> _canExecute;
   9         private readonly Action<object> _execute;
  10 
  11         public event EventHandler CanExecuteChanged;
  12 
  13         public DelegateCommand(Action<object> execute, Predicate<object> canExecute)
  14         {
  15             _execute = execute;
  16             _canExecute = canExecute;
  17         }
  18 
  19         public bool CanExecute(object parameter)
  20         {
  21             return _canExecute == null || _canExecute(parameter);
  22         }
  23 
  24         public void Execute(object parameter)
  25         {
  26             _execute(parameter);
  27         }
  28 
  29         public void RaiseCanExecuteChanged()
  30         {
  31             if (CanExecuteChanged != null)
  32             {
  33                 CanExecuteChanged(this, EventArgs.Empty);
  34             }
  35         }
  36     }
  37 }