Develop Reference

WPF C# ListBox IsMouseOver and IsSelected background

I am have made the following usercontrol, and all works well except the 2 Background setter properties with value transparent for both isMouseOver and IsSelected that do nothing..
<UserControl.Resources>
<DataTemplate x:Key="DeviceItemTemplate">
<Border Padding="10,5" Margin="10" BorderThickness="4" BorderBrush="Green" CornerRadius="20" Height="150" Width="150">
<StackPanel Orientation="Vertical">
<TextBox Name="screenNameTextBox"
Margin="10" Height="20"
Text="{Binding Name}" />
<TextBox
Margin="10" Height="20"
Text="{Binding Location}" />
</StackPanel>
</Border>
</DataTemplate>
<DataTemplate x:Key="DeviceItemTemplateSelected">
<Border Padding="10,5" Margin="10" BorderThickness="4" BorderBrush="Orange" CornerRadius="20" Height="150" Width="150" >
<StackPanel Orientation="Vertical" >
<TextBox Name="screenNameTextBox"
Margin="10" Height="20"
Text="{Binding Name}" />
<TextBox
Margin="10" Height="20"
Text="{Binding Location}" />
</StackPanel>
</Border>
</DataTemplate>
<Style TargetType="{x:Type ListBoxItem}" x:Key="DeviceContainerStyle">
<Setter Property="ContentTemplate" Value="{DynamicResource DeviceItemTemplate}"/>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True" >
<Setter Property="BorderThickness" Value="0" />
<Setter Property="Background" Value="Transparent" />
</Trigger>
<Trigger Property="IsSelected" Value="True">
<Setter Property="ContentTemplate" Value="{DynamicResource DeviceItemTemplateSelected}"/>
<Setter Property="BorderThickness" Value="0" />
<Setter Property="Background" Value="Transparent" />
</Trigger>
</Style.Triggers>
</Style>
</UserControl.Resources>
<Border
Grid.Column="0"
Margin="10"
BorderBrush="Silver"
BorderThickness="1">
<ListBox ItemsSource="{Binding Devices, UpdateSourceTrigger=PropertyChanged}"
SelectedItem="{Binding SelectedScreen, Mode=TwoWay}"
ItemContainerStyle="{StaticResource DeviceContainerStyle}"
ScrollViewer.HorizontalScrollBarVisibility="Disabled" >
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel IsItemsHost="True" Orientation="Horizontal" />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
</ListBox>
</Border>
This is how it looks
I also tried white, but got same results. I cannot get rid of this blue background.
What am I overlooking please?
-----After receiving mm8 answer-----
Placed all his code in a resource dictionary, made some changes to the solidcolorbrush and BorderThickness, and modified the style section from previous to:
<Style BasedOn="{StaticResource ListBoxItemSSDS}" TargetType="{x:Type ListBoxItem}" x:Key="DeviceContainerStyle">
<Setter Property="ContentTemplate" Value="{DynamicResource DeviceItemTemplate}"/>
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="ContentTemplate" Value="{DynamicResource DeviceItemTemplateSelected}"/>
</Trigger>
</Style.Triggers>
</Style>

You need to define a custom ControlTemplate for the ListBoxItem to be able to the background of it when the IsMouseOver and IsSelected properties are set.
You can right-click on a ListBoxItem in design mode in Visual Studio or in Blend and choose Edit Template->Edit a Copy to copy the default template into your XAML markup and then edit it as per your requirements.
Here is what it looks like and the resources that are involved:
<Style x:Key="FocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Margin="2" SnapsToDevicePixels="true" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<SolidColorBrush x:Key="Item.MouseOver.Background" Color="#1F26A0DA"/>
<SolidColorBrush x:Key="Item.MouseOver.Border" Color="#a826A0Da"/>
<SolidColorBrush x:Key="Item.SelectedInactive.Background" Color="#3DDADADA"/>
<SolidColorBrush x:Key="Item.SelectedInactive.Border" Color="#FFDADADA"/>
<SolidColorBrush x:Key="Item.SelectedActive.Background" Color="#3D26A0DA"/>
<SolidColorBrush x:Key="Item.SelectedActive.Border" Color="#FF26A0DA"/>
<Style x:Key="ListBoxItemStyle1" TargetType="{x:Type ListBoxItem}">
<Setter Property="SnapsToDevicePixels" Value="True"/>
<Setter Property="Padding" Value="4,1"/>
<Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListBoxItem}">
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Border>
<ControlTemplate.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.MouseOver.Background}"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.MouseOver.Border}"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="Selector.IsSelectionActive" Value="False"/>
<Condition Property="IsSelected" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Background}"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Border}"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="Selector.IsSelectionActive" Value="True"/>
<Condition Property="IsSelected" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Background}"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Border}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="TextElement.Foreground" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
You may for example change the Color of the Item.MouseOver.Background and Item.SelectedActive.Background resources.

Accessing the border around a contentpresenter

I have a ListView which uses a DataTemplate. When an item is selected a border and background is added but I am unsure where from. This shows in the visual tree as a border around the ContentPresenter but inside the ListViewItem. The properties show that they were added by triggers in the TemplatedParent template. How can I override these triggers given the structure below or is my approach wrong?
<ListView x:Name="MyListview" ItemsSource="{Binding Thumbnails}" ScrollViewer.HorizontalScrollBarVisibility="Disabled">
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<local:VirtualizingWrapPanel IsItemsHost="True" ....../>
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="SnapsToDevicePixels" Value="true" />
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemTemplate>
<DataTemplate x:Name="ThumbItemTemplate" DataType="{x:Type local:ThumbItem}">
<Grid Margin="6" Width="128" Height="168">
<Grid.RowDefinitions>
<RowDefinition Height="128"></RowDefinition>
<RowDefinition></RowDefinition>
</Grid.RowDefinitions>
<Border Grid.Row="0" BorderThickness="0">
<Image x:Name="ThumbnailImage" MaxHeight="128" MaxWidth="128" Source="{Binding Thumbnail}" />
</Border>
<TextBlock Grid.Row="1" Margin="0,6,0,0" TextAlignment="Center" x:Name="Description" Text="{Binding Title}" />
</Grid>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>

These come from the ItemContainerStyle. You could define your own custom template for the ListViewItem, e.g:
<Style TargetType="ListViewItem">
<Style.Resources>
<Style x:Key="FocusVisual">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Margin="2" SnapsToDevicePixels="true" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<SolidColorBrush x:Key="Item.MouseOver.Background" Color="#1F26A0DA"/>
<SolidColorBrush x:Key="Item.MouseOver.Border" Color="#a826A0Da"/>
<SolidColorBrush x:Key="Item.SelectedInactive.Background" Color="#3DDADADA"/>
<SolidColorBrush x:Key="Item.SelectedInactive.Border" Color="#FFDADADA"/>
<SolidColorBrush x:Key="Item.SelectedActive.Background" Color="#3D26A0DA"/>
<SolidColorBrush x:Key="Item.SelectedActive.Border" Color="#FF26A0DA"/>
</Style.Resources>
<Setter Property="SnapsToDevicePixels" Value="True"/>
<Setter Property="Padding" Value="4,1"/>
<Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ListViewItem">
<Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
<ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Border>
<ControlTemplate.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.MouseOver.Background}"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.MouseOver.Border}"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="Selector.IsSelectionActive" Value="False"/>
<Condition Property="IsSelected" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Background}"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Border}"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="Selector.IsSelectionActive" Value="True"/>
<Condition Property="IsSelected" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Background}"/>
<Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Border}"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="TextElement.Foreground" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
You can copy the default template by right-clicking on a ListBox in design mode in Visual Studio and choose Edit Additional Templates->Edit Generated Item Container (ItemContainerStyle).

Changing TabItem Style To a TabControl.ItemTemplate

Could someone please help me.
I have a already written style for a TabItem Header.
But because my TabItem Header are binded I needed to use
TabControl.ItemTemplate instead of TabItem Header
So how do I even start getting the same style on a TabControl.ItemTemplate that I have for the TabItem
So I had this:
<TabItem Header="Tab1" Style="{StaticResource TabStyle}">
</TabItem>
Now I have this:
<TabControl.ItemTemplate>
<!-- this is the header template-->
<DataTemplate>
<TextBlock Text="{Binding Person}" />
</DataTemplate>
</TabControl.ItemTemplate>
This is the Style for the original TabItem:
<Style x:Key="TabStyle" TargetType="{x:Type TabItem}">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabItem}">
<Border Padding="3">
<Grid Name ="grid" Height="24">
<Border Name="BorderName"
CornerRadius="12,12,12,12"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}" />
<Rectangle Name="TabItemBackgorund"
RadiusX="12"
RadiusY="12"
Fill="{StaticResource TabItemBackgroundBrush}">
</Rectangle>
<Border Name="border"
BorderThickness="{TemplateBinding BorderThickness}"
Padding="{TemplateBinding Padding}">
<ContentPresenter Name="TabItemTextbox"
ContentSource="Header"
Margin="6,0,6,0"
TextBlock.Foreground="{StaticResource TabItemBackgroundBrush}"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
</Border>
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter TargetName="TabItemBackgorund" Property="Fill" Value="#00bfc2" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.Foreground" Value="#ffffff" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.FontWeight" Value="Bold" />
</Trigger>
<Trigger Property="IsSelected" Value="False">
<Setter TargetName="TabItemBackgorund" Property="Fill" Value="{StaticResource TabItemBackgroundBrush}" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.Foreground" Value="#9494a3" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.FontWeight" Value="Bold" />
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter TargetName="TabItemBackgorund" Property="Fill" Value="#00bfc2" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.Foreground" Value="#ffffff" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.FontWeight" Value="Bold" />
</Trigger>
<Trigger SourceName="grid" Property="IsMouseOver" Value="True">
<Setter TargetName="TabItemBackgorund" Property="Fill" Value="#FF4F78" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.Foreground" Value="#ffffff" />
<Setter TargetName="TabItemTextbox" Property="TextBlock.FontWeight" Value="Bold" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

I have a already written style for a TabItem Header. But because my
TabItem Header are binded I needed to use TabControl.ItemTemplate
instead of TabItem Header
Instead of Header="Tab1" in TabItem, you could continue using your original TabItem's Style with a Header Setter
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="Header" Value="{Binding Person}"/>
<Setter Property="Template">
and apply the style to TabControl.ItemContainerStyle
<TabControl>
<TabControl.ItemContainerStyle>
<Style TargetType="TabItem">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="Header" Value="{Binding Person}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabItem}">
...
</Style>
</TabControl.ItemContainerStyle>
</TabControl>

Bug in WPF user control

I created a user control with a menu in WPF. It was working just fine and now I'm seeing a format issue with the MenuItem.Header. Basically if I add a header where the name has a "_" character it deletes it. For instance, if I add this to the header: "Test_Header_Name," it shows as: "TestHeader_Name." So basically it formats/manipulates the string and deletes the first "_" character. I know things don't just happened out of the blue. I am sure, I must have done something at some point to change the format... but I cannot figure out what it was.
Here is the C# to test the menu:
public partial class MenuControl : UserControl
{
public MenuControl()
{
InitializeComponent();
MenuItem main = new MenuItem();
main.Header = "Sum(Test_Header_Name)";
for (int i = 0; i < 10; i++)
{
main.Items.Add("Test_" + i);
}
main.Items.Add(new Separator());
main.Items.Add("Remove");
this.PrincipalMenu.Items.Add(main);
}
}
And this is the XAML (which is where I think it is happening):
<UserControl x:Class="WindowsFormsApplication1.MenuControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="41" d:DesignWidth="380">
<UserControl.Resources>
<!--**************************
* STYLE: MenuItem
************************** -->
<SolidColorBrush x:Key="HighlightedBackgroundBrush" Color="#FFDEDEDE" />
<SolidColorBrush x:Key="MenuBackgroundBrush" Color="White" />
<SolidColorBrush x:Key="NormalBorderBrush" Color="#FFE5DFDF" />
<SolidColorBrush x:Key="SolidMenuFontBrush" Color="Black" />
<SolidColorBrush x:Key="HighlightedText" Color="White" />
<SolidColorBrush x:Key="menuItemBrush" Color="#FFB7B7B7" />
<SolidColorBrush x:Key="WindowBackgroundBrush" Color="#FFF" />
<SolidColorBrush x:Key="SolidBorderBrush" Color="#888" />
<Style x:Key="{x:Type Menu}" TargetType="{x:Type Menu}">
<Setter Property="OverridesDefaultStyle" Value="True"/>
<Setter Property="SnapsToDevicePixels" Value="True"/>
<Setter Property="Height" Value="25"/>
<Setter Property="Foreground" Value="{StaticResource SolidMenuFontBrush}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Menu}">
<Border
Background="{StaticResource MenuBackgroundBrush}"
BorderBrush="{StaticResource MenuBackgroundBrush}"
BorderThickness="1">
<StackPanel ClipToBounds="True" Orientation="Horizontal" IsItemsHost="True"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="{x:Type MenuItem}" TargetType="{x:Type MenuItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type MenuItem}">
<Border x:Name="Border" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="0">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition x:Name="Col0" MinWidth="17" Width="Auto" SharedSizeGroup="MenuItemIconColumnGroup"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="MenuTextColumnGroup"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="MenuItemIGTColumnGroup"/>
<ColumnDefinition x:Name="Col3" Width="14"/>
</Grid.ColumnDefinitions>
<!-- ContentPresenter to show an Icon if needed -->
<ContentPresenter Grid.Column="0" Margin="4,0,6,0" x:Name="Icon" VerticalAlignment="Center" ContentSource="Icon"/>
<!-- Glyph is a checkmark if needed for a checkable menu -->
<Grid Grid.Column="0" Visibility="Hidden" Margin="4,0,6,0" x:Name="GlyphPanel" VerticalAlignment="Center">
<Path x:Name="GlyphPanelpath" VerticalAlignment="Center" Fill="{TemplateBinding Foreground}" Data="M0,2 L0,4.8 L2.5,7.4 L7.1,2.8 L7.1,0 L2.5,4.6 z" FlowDirection="LeftToRight"/>
</Grid>
<!-- Content for the menu text etc -->
<ContentPresenter Grid.Column="1" Margin="{TemplateBinding Padding}" x:Name="HeaderHost" RecognizesAccessKey="True" ContentSource="Header"/>
<!-- Content for the menu IGT -->
<ContentPresenter Grid.Column="2" Margin="8,1,8,1" x:Name="IGTHost" ContentSource="InputGestureText" VerticalAlignment="Center"/>
<!-- Arrow drawn path which points to the next level of the menu -->
<Grid Grid.Column="3" Margin="4,0,6,0" x:Name="ArrowPanel" VerticalAlignment="Center">
<Path x:Name="ArrowPanelPath" HorizontalAlignment="Right" VerticalAlignment="Center" Fill="{TemplateBinding Foreground}" Data="M0,0 L0,8 L4,4 z"/>
</Grid>
<!--IsOpen="{Binding Path=IsSubmenuOpen, RelativeSource={RelativeSource TemplatedParent}}"
PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}"
-->
<!-- The Popup is the body of the menu which expands down or across depending on the level of the item -->
<Popup Placement="Right" IsOpen="{TemplateBinding IsSubmenuOpen}" x:Name="SubMenuPopup" Focusable="false" PopupAnimation="Fade">
<Border x:Name="SubMenuBorder" SnapsToDevicePixels="True" Background="{StaticResource WindowBackgroundBrush}" BorderBrush="{StaticResource SolidBorderBrush}" BorderThickness="1" Padding="2,2,2,2">
<Grid x:Name="SubMenu" Grid.IsSharedSizeScope="True">
<!--StackPanel holds children of the menu. This is set by IsItemsHost=True-->
<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle"/>
<!--<ScrollViewer CanContentScroll="True">
<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" />
</ScrollViewer>-->
</Grid>
</Border>
</Popup>
</Grid>
</Border>
<!-- These triggers re-configure the four arrangements of MenuItem to show different levels of menu via Role -->
<ControlTemplate.Triggers>
<!-- Role = TopLevelHeader : this is the root menu item in a menu; the Popup expands down
2/6/2013 Luis Garcia
-->
<!--<Trigger Property="Role" Value="TopLevelHeader">
<Setter Property="Padding" Value="6,1,6,1"/>
<Setter Property="Placement" Value="Bottom" TargetName="SubMenuPopup"/>
<Setter Property="MinWidth" Value="0" TargetName="Col0"/>
<Setter Property="Width" Value="Auto" TargetName="Col3"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="GlyphPanel"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="IGTHost"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>-->
<!-- Role = TopLevelItem : this is a child menu item from the top level without any child items-->
<Trigger Property="Role" Value="TopLevelItem">
<Setter Property="Padding" Value="6,1,6,1"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<!-- Role = SubMenuHeader : this is a child menu item which does not have children -->
<Trigger Property="Role" Value="SubmenuHeader">
<Setter Property="DockPanel.Dock" Value="Top"/>
<Setter Property="Padding" Value="0,2,0,2"/>
</Trigger>
<!-- Role = SubMenuItem : this is a child menu item which has children-->
<Trigger Property="Role" Value="SubmenuItem">
<Setter Property="DockPanel.Dock" Value="Top"/>
<Setter Property="Padding" Value="0,2,0,2"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<Trigger Property="IsSuspendingPopupAnimation" Value="true">
<Setter Property="PopupAnimation" Value="None" TargetName="SubMenuPopup"/>
</Trigger>
<!-- If no Icon is present the we collapse the Icon Content -->
<Trigger Property="Icon" Value="{x:Null}">
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
</Trigger>
<!-- The GlyphPanel contains the CheckMark -->
<Trigger Property="IsChecked" Value="true">
<Setter Property="Visibility" Value="Visible" TargetName="GlyphPanel"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
</Trigger>
<!-- Using the system colors for the Menu Highlight and IsEnabled-->
<Trigger Property="IsHighlighted" Value="true">
<Setter Property="Background" Value="{StaticResource HighlightedBackgroundBrush}" TargetName="Border"/>
<Setter Property="Foreground" Value="{StaticResource HighlightedText}"/>
<Setter Property="BorderBrush" Value="{StaticResource NormalBorderBrush}" TargetName="Border"/>
</Trigger>
<Trigger Property="IsHighlighted" Value="false">
<Setter Property="Background" Value="{StaticResource MenuBackgroundBrush}" TargetName="Border"/>
<Setter Property="Foreground" Value="{StaticResource SolidMenuFontBrush}"/>
<Setter Property="BorderBrush" Value="{StaticResource MenuBackgroundBrush}" TargetName="Border"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="LightGray"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</UserControl.Resources>
<UserControl.Foreground>
<SolidColorBrush />
</UserControl.Foreground>
<Grid Height="24" Width="250" HorizontalAlignment="Left">
<Grid.Background>
<SolidColorBrush />
</Grid.Background>
<Menu Name="PrincipalMenu" Margin="0,0,-100,0">
</Menu>
</Grid>
Any help is greatly appreciated!

Underscores are used in WPF Content controls as accelerator keys.
So adding "E_dit" to a content control causes the "d" to be underlined at runtime.
The user can press ALT-D to move focus to the control.
In your case "Test_Header_Name" it's the "H" is prefixed by the underscore, so it is the accelerator key.
The solution is to use two underscores "__" to stop the accelerator key addition.

My guess is that the first underscore is being turned into an AccessKey for the MenuItem since you are using it in the Header. So in the example above, you probably have an AccessKey of 'h' for your MenuItem. See this answer for more on the subject.
I'm not sure if there's a way to override the behavior, perhaps if you use the ascii code for the underscore or something.

WPF C# - Change the brush of a menu's background

Does anyone know how to change the brush for a menu's background? This sounds simple, but I don't see any obvious way to do this. You'd think that the Background property would change it, but it doesn't.
Here's what my menu looks like (notice the default white background):
Example Code:
<Window x:Class="WpfApplication1.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300">
<Window.Resources>
<SolidColorBrush x:Key="menuItemBrush"
Color="#FF505050" />
</Window.Resources>
<Grid x:Name="mainGrid"
Background="#FF252525">
<Menu x:Name="mainMenu"
Background="{DynamicResource menuItemBrush}"
Grid.ColumnSpan="2"
VerticalAlignment="Top">
<MenuItem x:Name="fileMenu"
Background="{DynamicResource menuItemBrush}"
Foreground="White"
Header="File">
<MenuItem x:Name="fileOpenMenuItem"
Background="{DynamicResource menuItemBrush}"
Foreground="White"
Header="Open..." />
<MenuItem x:Name="fileSaveMenuItem"
Background="{DynamicResource menuItemBrush}"
Foreground="White"
Header="Save" />
<MenuItem x:Name="fileSaveAsMenuItem"
Background="{DynamicResource menuItemBrush}"
Foreground="White"
Header="Save As..." />
<Separator Style="{DynamicResource menuItemSeperator}" />
<MenuItem x:Name="fileExitMenuItem"
Background="{DynamicResource menuItemBrush}"
Foreground="White"
Header="Exit" />
</MenuItem>
</Menu>
</Grid>

I'd suggest using a tool called kaxaml for writing styles. It includes several code snippets, a color picker and a nice way to instantly see what changes in the xaml code does. Here is a full menu style for what you are trying to do. Just change the brush colors at the top to suit to your needs.
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Page.Resources>
<!--**************************
* STYLE: MenuItem
************************** -->
<SolidColorBrush x:Key="HighlightedBackgroundBrush" Color="#FF797878" />
<SolidColorBrush x:Key="MenuBackgroundBrush" Color="#FF505050" />
<SolidColorBrush x:Key="NormalBorderBrush" Color="#FFFFFFFF" />
<SolidColorBrush x:Key="SolidMenuFontBrush" Color="#FFFFFFFF" />
<SolidColorBrush x:Key="HighlightedText" Color="#FFFFFFFF" />
<Style x:Key="{x:Type Menu}" TargetType="{x:Type Menu}">
<Setter Property="OverridesDefaultStyle" Value="True"/>
<Setter Property="SnapsToDevicePixels" Value="True"/>
<Setter Property="Height" Value="25"/>
<Setter Property="Foreground" Value="{StaticResource SolidMenuFontBrush}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Menu}">
<Border
Background="{StaticResource MenuBackgroundBrush}"
BorderBrush="{StaticResource MenuBackgroundBrush}"
BorderThickness="1">
<StackPanel ClipToBounds="True" Orientation="Horizontal" IsItemsHost="True"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="{x:Type MenuItem}" TargetType="{x:Type MenuItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type MenuItem}">
<Border x:Name="Border"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="1">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition x:Name="Col0" MinWidth="17" Width="Auto" SharedSizeGroup="MenuItemIconColumnGroup"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="MenuTextColumnGroup"/>
<ColumnDefinition Width="Auto" SharedSizeGroup="MenuItemIGTColumnGroup"/>
<ColumnDefinition x:Name="Col3" Width="14"/>
</Grid.ColumnDefinitions>
<!-- ContentPresenter to show an Icon if needed -->
<ContentPresenter Grid.Column="0" Margin="4,0,6,0" x:Name="Icon" VerticalAlignment="Center" ContentSource="Icon"/>
<!-- Glyph is a checkmark if needed for a checkable menu -->
<Grid Grid.Column="0" Visibility="Hidden" Margin="4,0,6,0" x:Name="GlyphPanel" VerticalAlignment="Center">
<Path x:Name="GlyphPanelpath" VerticalAlignment="Center" Fill="{TemplateBinding Foreground}" Data="M0,2 L0,4.8 L2.5,7.4 L7.1,2.8 L7.1,0 L2.5,4.6 z" FlowDirection="LeftToRight"/>
</Grid>
<!-- Content for the menu text etc -->
<ContentPresenter Grid.Column="1"
Margin="{TemplateBinding Padding}"
x:Name="HeaderHost"
RecognizesAccessKey="True"
ContentSource="Header"/>
<!-- Content for the menu IGT -->
<ContentPresenter Grid.Column="2"
Margin="8,1,8,1"
x:Name="IGTHost"
ContentSource="InputGestureText"
VerticalAlignment="Center"/>
<!-- Arrow drawn path which points to the next level of the menu -->
<Grid Grid.Column="3" Margin="4,0,6,0" x:Name="ArrowPanel" VerticalAlignment="Center">
<Path x:Name="ArrowPanelPath" HorizontalAlignment="Right" VerticalAlignment="Center" Fill="{TemplateBinding Foreground}" Data="M0,0 L0,8 L4,4 z"/>
</Grid>
<!-- The Popup is the body of the menu which expands down or across depending on the level of the item -->
<Popup IsOpen="{Binding Path=IsSubmenuOpen, RelativeSource={RelativeSource TemplatedParent}}" Placement="Right" x:Name="SubMenuPopup" Focusable="false" PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}">
<Border x:Name="SubMenuBorder" BorderBrush="{Binding Path=Foreground, RelativeSource={RelativeSource AncestorType={x:Type Menu}}}" BorderThickness="1" Padding="2,2,2,2">
<Grid x:Name="SubMenu" Grid.IsSharedSizeScope="True">
<!-- StackPanel holds children of the menu. This is set by IsItemsHost=True -->
<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle"/>
</Grid>
</Border>
</Popup>
</Grid>
</Border>
<!-- These triggers re-configure the four arrangements of MenuItem to show different levels of menu via Role -->
<ControlTemplate.Triggers>
<!-- Role = TopLevelHeader : this is the root menu item in a menu; the Popup expands down -->
<Trigger Property="Role" Value="TopLevelHeader">
<Setter Property="Padding" Value="6,1,6,1"/>
<Setter Property="Placement" Value="Bottom" TargetName="SubMenuPopup"/>
<Setter Property="MinWidth" Value="0" TargetName="Col0"/>
<Setter Property="Width" Value="Auto" TargetName="Col3"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="GlyphPanel"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="IGTHost"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<!-- Role = TopLevelItem : this is a child menu item from the top level without any child items-->
<Trigger Property="Role" Value="TopLevelItem">
<Setter Property="Padding" Value="6,1,6,1"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<!-- Role = SubMenuHeader : this is a child menu item which does not have children -->
<Trigger Property="Role" Value="SubmenuHeader">
<Setter Property="DockPanel.Dock" Value="Top"/>
<Setter Property="Padding" Value="0,2,0,2"/>
</Trigger>
<!-- Role = SubMenuItem : this is a child menu item which has children-->
<Trigger Property="Role" Value="SubmenuItem">
<Setter Property="DockPanel.Dock" Value="Top"/>
<Setter Property="Padding" Value="0,2,0,2"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="ArrowPanel"/>
</Trigger>
<Trigger Property="IsSuspendingPopupAnimation" Value="true">
<Setter Property="PopupAnimation" Value="None" TargetName="SubMenuPopup"/>
</Trigger>
<!-- If no Icon is present the we collapse the Icon Content -->
<Trigger Property="Icon" Value="{x:Null}">
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
</Trigger>
<!-- The GlyphPanel contains the CheckMark -->
<Trigger Property="IsChecked" Value="true">
<Setter Property="Visibility" Value="Visible" TargetName="GlyphPanel"/>
<Setter Property="Visibility" Value="Collapsed" TargetName="Icon"/>
</Trigger>
<!-- Using the system colors for the Menu Highlight and IsEnabled-->
<Trigger Property="IsHighlighted" Value="true">
<Setter Property="Background" Value="{StaticResource HighlightedBackgroundBrush}" TargetName="Border"/>
<Setter Property="Foreground" Value="{StaticResource HighlightedText}"/>
<Setter Property="BorderBrush" Value="{StaticResource NormalBorderBrush}" TargetName="Border"/>
</Trigger>
<Trigger Property="IsHighlighted" Value="false">
<Setter Property="Background" Value="{StaticResource MenuBackgroundBrush}" TargetName="Border"/>
<Setter Property="Foreground" Value="{StaticResource SolidMenuFontBrush}"/>
<Setter Property="BorderBrush" Value="{StaticResource MenuBackgroundBrush}" TargetName="Border"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="LightGray"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Page.Resources>
<Grid x:Name="mainGrid"
Background="#FF252525">
<Menu x:Name="mainMenu"
Grid.ColumnSpan="2"
VerticalAlignment="Top">
<MenuItem x:Name="fileMenu"
Header="File">
<MenuItem x:Name="fileOpenMenuItem"
Header="Open..." />
<MenuItem x:Name="fileSaveMenuItem"
Header="Save" />
<MenuItem x:Name="fileSaveAsMenuItem"
Background="{DynamicResource menuItemBrush}"
Header="Save As..." />
</MenuItem>
</Menu>
</Grid>
</Page>

You can't do it without overriding the template for the menu item. Deep inside the template is a control called "Part_Popup". You need to change it's background color.