public MessageViewer(ChatListChatItemVM chatItem)
 {
     this.InitializeComponent();
     this.MessageViewerList.DataContext = this;
     VM = new MessageViewerViewModel(chatItem);
 }
 public MessageViewer()
 {
     this.InitializeComponent();
     this.MessageViewerList.DataContext = this;
     VM = new MessageViewerViewModel();
 }