private void DataContextChangedEventHandler(object sender, DependencyPropertyChangedEventArgs e)
 {
     if (DataContext != null && DataContext is SprintViewModel)
     {
         _viewModel = DataContext as SprintViewModel;
         //_viewModel.PropertyChanged += ViewModelPropertyChangedEventHandler;
         _viewModel.SetDialog  += ShowDialogEventHandler;
         _viewModel.HideDialog += HideDialogEventHandler;
         CheckDialogsState();
     }
 }
        public SprintView()
        {
            InitializeComponent();
            InitializeDialogs();

            if (DataContext is SprintViewModel)
            {
                _viewModel = DataContext as SprintViewModel;
                //_viewModel.PropertyChanged += ViewModelPropertyChangedEventHandler;
                _viewModel.SetDialog  += ShowDialogEventHandler;
                _viewModel.HideDialog += HideDialogEventHandler;
                CheckDialogsState();
            }
            else
            {
                DataContextChanged += new DependencyPropertyChangedEventHandler(DataContextChangedEventHandler);
            }
        }