ContextMenu

ContextMenu without CompositeCollection

You can use the ContextMenu as you are familiar with it:

<ContextMenu>
  <MenuItem Command="ApplicationCommands.New" />
  <MenuItem Command="ApplicationCommands.Delete" />
  <MenuItem Command="ApplicationCommands.Print" />
</ContextMenu>

ContextMenu with CompositeCollection

If you want to use a part of the ContextMenu which is declared as resource and is shared you have to use a CompositeCollection as follwos:

<CompositeCollection x:Key="ContextMenuBase"
                     x:Shared="False">
  <MenuItem Command="ApplicationCommands.New" />
  <MenuItem Command="ApplicationCommands.Delete" />
  <Separator />
  <StaticResource ResourceKey="ContextMenuItemRefresh" />
  <Separator />
</CompositeCollection>


<ContextMenu>
  <ContextMenu.ItemsSource>
    <CompositeCollection>
      <CollectionContainer Collection="{StaticResource ContextMenuBase}"></CollectionContainer>
      <MenuItem Command="ApplicationCommands.Print" />
    </CompositeCollection>
  </ContextMenu.ItemsSource>
</ContextMenu>

When you run the application you get a lot of binding errors:

System.Windows.Data Error: 4 : Cannot find source for binding with reference ‘RelativeSource FindAncestor, AncestorType=’System.Windows.Controls.ItemsControl’, AncestorLevel=’1’’. BindingExpression:Path=VerticalContentAlignment; DataItem=null; target element is ‘MenuItem’ (Name=’’); target property is ‘VerticalContentAlignment’ (type ‘VerticalAlignment’)

This is a known issue in WPF and a workaround is to create a custom MenuItem style:

<Style TargetType="{x:Type MenuItem}"
       BasedOn="{StaticResource MetroMenuItem}">
  <Setter Property="HorizontalContentAlignment"
          Value="Left" />
  <Setter Property="VerticalContentAlignment"
          Value="Center" />
  </Style>

The drawback is that you loose the ability to contol the content-alignment of the MenuItem by setting the content-alignment properties on a ContextMenu.