c# - WPF ContextMenu itemtemplate, menuitem inside menuitem

Question

I have the following xaml:

<ContextMenu ItemsSource="{Binding TestItems}">
     <ContextMenu.ItemTemplate>
          <DataTemplate DataType="models:TestItemModel">
              <MenuItem IsChecked="{Binding IsSelected}" Header="{Binding Header}"  />
          </DataTemplate>
     </ContextMenu.ItemTemplate>
</ContextMenu>

The TestItemModel class only consists of a IsSelected boolean property and a Header string property.

TestItems is a list of TestItemModels.

The data is binded to the contextmenu but it is reflected in the UI as a MenuItem inside a MenuItem (with the additional margins as such, making the menu very big). I can fix this by changing the MenuItem inside the DataTemplate to a TextBox, but then I cannot bind the IsSelected anymore (which I need for visualization properties).

There are a couple of questions I have regarding this:

• Why is there a MenuItem inside a MenuItem? This doesn't make sense to me as it's not binded to a menuitem list but to a list of TestItemModels.
• How can I resolve this?

Answer 1

Because MenuItem is the container type and when it translates your view model into visual item it will wrap your template in MenuItem. In the same way ListBox will create ListBoxItem or ListView will use ListViewItem. To bind properties of the wrapper you need to use ItemContainerStyle

<ContextMenu ItemsSource="{Binding TestItems}">
   <ContextMenu.ItemContainerStyle>
      <Style TargetType="{x:Type MenuItem}">
         <Setter Property="IsChecked" Value="{Binding IsSelected}"/>
         <Setter Property="Header" Value="{Binding Header}"/>
      </Style>
   </ContextMenu.ItemContainerStyle>
</ContextMenu>

or, if you prefer, you can do it partially with ItemTemplate and ItemContainerStyle

<ContextMenu ItemsSource="{Binding TestItems}">
   <ContextMenu.ItemTemplate>
      <DataTemplate>
         <TextBlock Text="{Binding Header}"/>
      </DataTemplate>
   </ContextMenu.ItemTemplate>
   <ContextMenu.ItemContainerStyle>
      <Style TargetType="{x:Type MenuItem}">
         <Setter Property="IsChecked" Value="{Binding IsSelected}"/>
      </Style>
   </ContextMenu.ItemContainerStyle>
</ContextMenu>

In this scenario whatever is in ItemTemplate will become MenuItem.Header but IsChecked property still needs to be bound in ItemContainerStyle