WPF: Nested MenuItems in a ToolBar

Question

I am working on some XAML for a wpf application and I am having some trouble getting it to do what I want. Here is a sample of my XAML:

<!-- Tool Bar Tray -->
<ToolBarTray Name="toolBarTray1" DockPanel.Dock="Top">
    <!-- File And Edit Tools -->
    <ToolBar Name="toolBar1" Band="1" BandIndex="1">
        <!-- Regular Items -->
        <Button>A</Button>
        <Button>B</Button>
        <!-- Overflow Menu For Special Items -->
        <MenuItem ToolBar.OverflowMode="Always" Header="Special Items">
            <MenuItem Header="C"/>
            <MenuItem Header="D"/>
        </MenuItem>
    </ToolBar>
</ToolBarTray>

When I click on the overflow button of my toolbar, the "Special Items" MenuItem appears with a little arrow next to it, indicating nested elements. However, when I hover the mouse over "Special Items" or try to click on it, the MenuItems "C" and "D" are not being displayed.

I was hoping that MenuItem would just work outside of a Menu, but I tried to do the straight-forward thing, just in case. Including these MenuItems inside a Menu and, instead, giving this Menu the ToolBar.OverflowMode="Always" property produces some unwanted styling. The arrow is no longer present, the "Special Items" entry needs to be clicked on to activate the sub-menu and the sub-menu positioning looks a little off.

Does anyone know what is going on?

Edit: Adding a menu to the overflow is producing exactly what I requested (big surprise). What I am after is a way to convert top-level headers and items to the sub-menu level. I have turned towards this control template example on MSDN for a solution (below).

Edit,Edit: @gcores (comment discussion): Really? Am I missing something?

<ToolBar Name="toolBar1" Band="1" BandIndex="4"> 
    <!-- Displayed Buttons -->
    <Button>A</Button>
    <Button>B</Button>
    <!-- Special Items Menu -->
    <Menu ToolBar.OverflowMode="Always" >
        <MenuItem Style="{StaticResource MenuItemStyle}" Header="Special">
            <MenuItem Header="C"/>
            <MenuItem Header="D"/>
        </MenuItem>
    </Menu>
</ToolBar>

This snippet doesn't work for me. I have to click on 'Special' for the sub-menu to display.

Answer 1

Another solution is to use the existing templates and override the Template for the TopLevelHeader with the Template of the SubmenuHeader.

<Style x:Key="MenuItemStyle" TargetType="{x:Type MenuItem}">
  <Style.Triggers>
    <Trigger Property="Role" Value="TopLevelHeader">
      <Setter Property="Template"
              Value="{StaticResource {x:Static MenuItem.SubmenuHeaderTemplateKey}}"/>
    </Trigger>
  </Style.Triggers> 
</Style>

And use this style in your top level MenuItem. That should simplify your code.

EDIT: You're right, it only works when you click on it (don't know how I convinced myself it worked, sorry :)). It's functionality is like a TopLevelMenu even though the Template says otherwise, its quite confusing.

Only thing I can think of is adding a Trigger to show the Submenu on IsMenuOver and handling the Click event so it does nothing but I don't know how well that would work.

Answer 2

After more reading, a solution I am using is below.

<!-- Resource Dictionary Stuff -->

<!-- Some Brushes -->
<SolidColorBrush x:Key="Brush_1"
    Color="White" />

<LinearGradientBrush x:Key="Brush_2"
    StartPoint="0 0"
    EndPoint="0 1">

    <GradientStop
        Color="White"
        Offset="0"/>

    <GradientStop 
        Color="DarkSeaGreen"
        Offset="1"/>

</LinearGradientBrush>

<SolidColorBrush x:Key="Brush_3"
    Color="DarkOliveGreen"/>

<!-- Custom MenuItem - Top Level Header - Style 1 -->
<Style x:Key="MenuItem_TLH_Style1"
    TargetType="MenuItem">

    <!--<EventSetter Event="PreviewMouseDown" Handler="DoNothing"/>-->

    <Setter Property="Template">
        <Setter.Value>

            <ControlTemplate x:Name="ControlTemplate"
                TargetType="MenuItem">

                <!-- A headered text that may display a submenu
                     on a trigger. This submenu is the host for a
                     menu item's items. -->
                <Border x:Name="BoundaryBorder"
                    Background="{StaticResource Brush_1}"
                    BorderThickness="1">

                    <Grid x:Name="ContainerGrid">

                        <ContentPresenter x:Name="HeaderContent"
                            Margin="6 3 6 3" 
                            ContentSource="Header"
                            RecognizesAccessKey="True"/>

                        <Popup x:Name="SubmenuPopup"
                            Placement="Bottom"
                            IsOpen="{TemplateBinding IsSubmenuOpen}"
                            AllowsTransparency="True"
                            Focusable="False"
                            PopupAnimation="Fade">

                            <Border x:Name="SubmenuBoundaryBorder"
                                SnapsToDevicePixels="True"
                                Background="{StaticResource Brush_1}"
                                BorderBrush="{StaticResource SolidBorderBrush}"
                                BorderThickness="1">

                                <StackPanel x:Name="ItemsStackPanel"
                                    IsItemsHost="True"
                                    KeyboardNavigation.DirectionalNavigation="Cycle"/>

                            </Border>
                        </Popup>
                    </Grid>
                </Border>

                <ControlTemplate.Triggers>

                    <!--  -->
                    <Trigger
                        Property="IsSuspendingPopupAnimation"
                        Value="true">

                        <Setter 
                            TargetName="SubmenuPopup"
                            Property="PopupAnimation"
                            Value="Fade"/>

                    </Trigger>

                    <!-- On mouse-over, show the submenu and highlight the header. -->
                    <Trigger 
                        Property="IsMouseOver"
                        Value="true">

                        <Setter 
                            TargetName="BoundaryBorder"
                            Property="Background"
                            Value="{StaticResource Brush_2}"/>

                        <Setter 
                            TargetName="BoundaryBorder"
                            Property="BorderBrush"
                            Value="{StaticResource Brush_3}"/>

                        <Setter
                            Property="IsSubmenuOpen"
                            Value="true"/>

                        <!-- sloppy? -->
                        <Setter
                            TargetName="SubmenuPopup"
                            Property="IsOpen"
                            Value="true"/>

                    </Trigger>

                    <Trigger 
                        SourceName="SubmenuPopup"
                        Property="AllowsTransparency"
                        Value="true">

                        <Setter 
                            TargetName="SubmenuBoundaryBorder"
                            Property="CornerRadius"
                            Value="0 0 4 4"/>

                        <Setter 
                            TargetName="SubmenuBoundaryBorder"
                            Property="Padding"
                            Value="0 0 0 3"/>

                    </Trigger>

                    <!-- Visually indicate an unaccessible menu item. -->
                    <Trigger
                        Property="IsEnabled"
                        Value="false">

                        <Setter 
                            Property="Foreground"
                            Value="{StaticResource DisabledForegroundBrush}"/>

                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

<!-- ... -->

<!-- Inside a window XAML file -->

<!-- Tool Bar Tray -->
<ToolBarTray x:Name="toolBarTray1"
    DockPanel.Dock="Top">

    <!-- File And Edit Tools -->
    <ToolBar x:Name="toolBar1" 
        Band="1" BandIndex="1">

        <!-- Displayed Buttons -->
        <Button x:Name="ButtonA"
            Content="A"/>

        <Button x:Name="ButtonB"
            Content="B"/>

        <!-- Overflow Menu For Special Items -->
        <Menu x:Name="OverflowMenu"
            ToolBar.OverflowMode="Always">

            <MenuItem x:Name="SpecialsMenuItem" 
                Style="{StaticResource MyStyle}"
                Header="Special Items">

                <MenuItem x:Name="CMenuItem"
                    Header="C">

                    <MenuItem x:Name="DMenuItem"
                        Header="D"/>

                </MenuItem>
            </MenuItem>
        </Menu>
    </ToolBar>
</ToolBarTray>

I attack the behavior of 'SubmenuPopup' on a mouse-over, rather than handling the click event. I'd like to understand this more fully, so I tried commenting out this part of the trigger and adding an event handler that calls a 'DoNothing()' method on the 'PreviewMouseDown' event. It turns out that I am missing something and I think it is related to focusing and/or how a menu handles its items collection. Not allowing an event to propagate after 'DoNothing()' (routedEventArgs.Handled = true) seems to eliminate the problems when clicking on the "Special Items" menu item. However, if one navigated away from the menu or added another menu item and then clicked on that, the hover behavior can be turned off or switched on and off.