private void btnExisting_Click(object sender, RoutedEventArgs e) { if (SelectedExistingTask != null && !string.IsNullOrWhiteSpace(_status.CurrentContextId)) { _taskService.AddContext(SelectedExistingTask.Id.ToString(), _status.CurrentContextId); if (null != this.PropertyChanged) { PropertyChanged(this, new PropertyChangedEventArgs(Utils <ViewContextPage> .MemberName(s => s.ContextTasks))); } } }