How can I debug data binding problems in MVVM?

Question

I rebuilt the Josh Smith CommandSink example from scratch and my version works without errors, except that my command buttons are inactive. I suppose this is because something is not installed correctly somewhere, so the commands will never be installed at CanExecute = trueor at some point will be installed at CanExecute = false.

But since data binding essentially takes place in XAML, I don’t know where to “set a breakpoint in the command” so that I can see at what time the button is assigned CanExecute = false or, for example. NOT assigned CanExecute = true.

Essentially, I have these command bindings in a view:

<UserControl.CommandBindings>
    <sink:CommandSinkBinding Command="vm:CustomerViewModel.CloseCommand"/>
    <sink:CommandSinkBinding Command="vm:CustomerViewModel.ShowInformationCommand"/>
</UserControl.CommandBindings>

and in my CustomerViewModel the command is defined as follows:

public static readonly RoutedCommand CloseCommand = new RoutedCommand();

public bool CanBeClosed
{
    get { return _customer.IsOpen; }
}

public void Close()
{
    _customer.IsOpen = false;

    this.OnPropertyChanged("CanBeClosed");
    this.OnPropertyChanged("CanBeApproved");
}

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, , Josh Smith , CommandSinkBinding.OnCommandSinkChanged:

if (!ConfigureDelayedProcessing(depObj, commandSink))
    ProcessCommandSinkChanged(depObj, commandSink);

Answer 1

:

XAML, dll WindowsBase XAML, PresentationTraceSources.TraceLevel. , .

XAML:

<TextBlock Text="{Binding someProperty, diagnostics:PresentationTraceSources.TraceLevel=High}"/>

:

, , , ! , , , , CanExe() " exe state", , " exe". , , ViewModel, :

, , someCommand.RaiseCanExecuteChanged();