Best way to set a MenuItem's sub-menu height?

Question

I currently have a menuitem (part of a context menu), with about ~35 menu items. Because of this, it causes the sub-menu to be huge. Even though I have scrolling ability, I woul

Answer 1

Unfortunately, WPF does not allow this to be modified by properties. You will have to modify the default ControlTemplate.

EDIT: I revised the blog entry on that here

Here is a sample (notice the addition of "MaxHeight" on "SubMenuScrollViewer"):

<Popup x:Name="PART_Popup"
    AllowsTransparency="true"
    Placement="Right"
    VerticalOffset="-3"
    HorizontalOffset="-2"
    IsOpen="{Binding Path=IsSubmenuOpen,RelativeSource={RelativeSource TemplatedParent}}"
    Focusable="false"
    PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}">
    <theme:SystemDropShadowChrome Name="Shdw" Color="Transparent">
        <ContentControl Name="SubMenuBorder"
            Template="{DynamicResource {ComponentResourceKey TypeInTargetAssembly={x:Type FrameworkElement}, ResourceId=SubmenuContent}}"
            IsTabStop="false">
            <ScrollViewer Name="SubMenuScrollViewer" CanContentScroll="true" MaxHeight="400" Style="{DynamicResource {ComponentResourceKey TypeInTargetAssembly={x:Type FrameworkElement}, ResourceId=MenuScrollViewer}}">
                <Grid RenderOptions.ClearTypeHint="Enabled">
                    <Canvas Height="0" Width="0" HorizontalAlignment="Left" VerticalAlignment="Top">
                        <Rectangle
                            Height="{Binding ElementName=SubMenuBorder,Path=ActualHeight}" 
                            Width="{Binding ElementName=SubMenuBorder,Path=ActualWidth}" 
                            Fill="{StaticResource SubMenuBackgroundBrush}" />
                    </Canvas>
                    <ItemsPresenter Name="ItemsPresenter" Margin="2"
                        KeyboardNavigation.TabNavigation="Cycle"
                        KeyboardNavigation.DirectionalNavigation="Cycle"
                        SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
                        Grid.IsSharedSizeScope="true"/>
                </Grid>
            </ScrollViewer>
        </ContentControl>
    </theme:SystemDropShadowChrome>
</Popup>

This is just to override the Aero theme. As you can see there is a lot of XAML for the MenuItem, so it's not graceful. Just make a separate ResourceDictionary to keep things tidy.