WPF/MVVM: Disable a Button's state when the ViewModel behind the UserControl is not yet Initialized?

Question

I have a DocumentListView.Xaml with a ListBox and 3 Buttons.

Behind that UserControl sits a DocumentListViewModel with 3 Buttons and their Command Property bound to

Answer 1

This is an interesting situation. Honestly I've never run into the case where the UI was loaded and interactive but the ViewModel was not yet bound.

However, ignoring that for a moment, you could potentially use a FallbackValue on your binding to bind to a globally available NullCommand or something that always returns false for its CanExecute method.

<Button Command="{Binding SaveCommand, FallbackValue={StaticResource NullCommand}}" />

Answer 2

Or you can use a Style for the button to disable:

<Style TargetType="{x:Type Button}" x:Key="DisablerButton">
    <Style.Triggers>
        <Trigger Property="Command" Value="{x:Null}">
            <Setter Property="IsEnabled" Value="False" />
        </Trigger>
    </Style.Triggers>
</Style>