Question

How do I bind the visibility of a button to a bool value in my ViewModel?

<Button Height="50" Width="50" Style="{StaticResource MyButtonStyle}"
    Command="{Binding SmallDisp}" CommandParameter="{Binding}" Cursor="Hand"
    Visibility="{Binding Path=AdvancedFormat}" />

Answer 1

Assuming AdvancedFormat is a bool, you need to declare and use a BooleanToVisibilityConverter:

<!-- In your resources section of the XAML -->
<BooleanToVisibilityConverter x:Key="BoolToVis" />

<!-- In your Button declaration -->
<Button
 Height="50" Width="50"
 Style="{StaticResource MyButtonStyle}"
 Command="{Binding SmallDisp}" CommandParameter="{Binding}" 
Cursor="Hand" Visibility="{Binding Path=AdvancedFormat, Converter={StaticResource BoolToVis}}"/>

Note the added Converter={StaticResource BoolToVis}.

This is a very common pattern when working with MVVM. In theory you could do the conversion yourself on the ViewModel property (i.e. just make the property itself of type Visibility) though I would prefer not to do that, since now you are messing with the separation of concerns. An item’s visbility should really be up to the View.