CanExecute未触发

Question

In my UWP the CanExecute handler doesn't get triggered. Here is my code:

RelayCommand

EditWorkItemEntry = new RelayCommand(async () =>
{
    var diag = new EditWorkItemEntryDialog(SelectedWorkItem);
    await diag.ShowAsync();
    await ReloadWorkItems();
}, () =>
{
    return SelectedWorkItem != null;
});

The code that uses the command:

<mt:MtPage.BottomAppBar>
  <CommandBar>
    <AppBarButton Icon="Edit" x:Uid="EditWorkItemEntry" Command="{x:Bind ViewModel.EditWorkItemEntry, Mode=OneWay}" />
  </CommandBar>
</mt:MtPage.BottomAppBar>

And the code that should trigger it:

<mtControls:DataGrid ItemsSource="{Binding WorkItems}" SelectedItem="{x:Bind ViewModel.SelectedWorkItem, Mode=OneWay}">
    <!-- More definition logic -->
</mtControls:DataGrid>

mtControls:DataGrid is mapped to MyToolkit DataGrid, it can be found here: https://github.com/MyToolkit/MyToolkit/tree/master/src/MyToolkit.Extended/Controls/DataGrid

Does anyone have an answer why it doesn't get called?

Answer 1

I encountered the same issue using GalaSoft.MvvmLight. Here is a workarround (just use the RaiseCanExecuteChanged() function of the RelayCommand):

private MyClass _selectedWorkItem;

public MyClass SelectedWorkItem
{
  get { return _selectedWorkItem; }
  set
  {
     _selectedWorkItem = value;
     EditWorkItemEntry.RaiseCanExecuteChanged();
  }
}

The problem is that the CommandManager is not present in UWP apps by design.