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Custom button border style does not change on IsPressed event

I'm trying to recreate a Valve VGUI interface style in WPF. So far I am able to assign a border to a button, but the border style does not change when pressing the button.
Here's my XAML code:
<Window.Resources>
<Style x:Key="BorderLight_Style" TargetType="Border">
<Setter Property="BorderBrush" Value="#889180" />
<Setter Property="BorderThickness" Value="1,1,0,0" />
</Style>
<Style x:Key="BorderShadow_Style" TargetType="Border">
<Setter Property="BorderBrush" Value="#FF282E22" />
<Setter Property="BorderThickness" Value="0,0,1,1" />
</Style>
<Style x:Key="BorderLight_Style_pressed" TargetType="Border">
<Setter Property="BorderBrush" Value="#FF282E22" />
<Setter Property="BorderThickness" Value="1,1,0,0" />
</Style>
<Style x:Key="BorderShadow_Style_pressed" TargetType="Border">
<Setter Property="BorderBrush" Value="#889180" />
<Setter Property="BorderThickness" Value="0,0,1,1" />
</Style>
<Style TargetType="Grid">
<Setter Property="Background" Value="#FF4C5844" />
</Style>
<Style TargetType="Button">
<Setter Property="Background" Value="#FF4C5844" />
<Setter Property="Foreground" Value="#D8DED3" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="Button">
<Border x:Name="border" Style="{StaticResource BorderShadow_Style}">
<Border x:Name="border2" Style="{StaticResource BorderLight_Style}" />
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsPressed" Value="True">
<Setter TargetName="border" Property="Style" Value="{StaticResource BorderShadow_Style_pressed}" />
<Setter TargetName="border2" Property="Style" Value="{StaticResource BorderLight_Style_pressed}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
Am I doing anything wrong with this? Thanks!

Controls need to have a defined Background property to participate in hit-testing - and thus to allow the IsPressed property to be set on a Button for example.
Set the Background property of your inner Border to any valid value - such as Transparent - to fix your Trigger.
Note: if you were to press TAB to select your button and press the space bar, you would see your Trigger working even though you didn't set it any background, because IsPressed also reacts to the space bar.

How to change TextAlignment of MetroAnimatedTabItem to center?

I am using MahApps.Metro for wpf UI. I want to change textalignment of MetroTabItem.
I set HorizontalContentAlignment to center. The below code is not working.
<metroControls:MetroAnimatedTabControl
metroControls:TabControlHelper.Underlined="SelectedTabItem"
ItemsSource="{Binding TabControlCollection}" SelectedIndex="0">
<metroControls:MetroAnimatedTabControl.Resources>
<Style TargetType="{x:Type metroControls:MetroTabItem}">
<Setter Property="metroControls:ControlsHelper.HeaderFontSize" Value="34"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="Width" Value="200"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Header" Value="{Binding Header}"/>
</Style>
How to center in this case?

Ok. I am solved this question.
I added some code in source. It is perfect working.
<Style TargetType="{x:Type metroControls:MetroTabItem}">
<Setter Property="metroControls:ControlsHelper.HeaderFontSize" Value="34"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="Width" Value="200"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="HeaderTemplate">
<Setter.Value>
<DataTemplate DataType="{x:Type TabItem}">
<TextBlock Text="{Binding Header}" HorizontalAlignment="Center"/>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>

How can I style only those Buttons which are in a DataGrid?

In App.xaml I have styled all my Buttons.
<Style TargetType="Button">
<Setter Property="Margin" Value="3"/>
</Style>
I realized if the Button is in a DataGrid then I not need a margin. I have a lot of DataGrid and I put this code into all of them one by one.
<DataGrid.Resources>
<Style TargetType="Button">
<Setter Property="Margin" Value="0"/>
</Style>
</DataGrid.Resources>
Is there a more clever way to do this?

You can define Style for DataGrid and within that, add child control style to particular modification.
If you want to add this Style to all the DataGrids, no need to defineKey.
<Style x:Key="dataGrid" TargetType="DataGrid">
<Style.Resources>
<Style TargetType="Button">
<Setter Property="Margin" Value="0" />
</Style>
</Style.Resources>
</Style>

Declare a style with the key in the Window.Resources or App.Resources as shown below.
<Window.Resources>
<Style TargetType="Button" x:Key="dataGridButtonStyle">
<Setter Property="Margin" Value="3"/>
<Setter Property="Background" Value="Wheat"/>
</Style>
</Window.Resources>
Then apply the style to the control using the StaticResource with the key(in this example key name is dataGridButtonStyle)
<Button Style="{StaticResource ResourceKey= dataGridButtonStyle}" Content="Hello"/>

Please add resource file at Windows or User control level so that it will apply all child controls as below,
<Window.Resources>
<Style TargetType="DataGrid">
<Style.Resources>
<Style TargetType="Button">
<Setter Property="Background" Value="Red" />
<Setter Property="Margin" Value="0" />
</Style>
</Style.Resources>
</Style>
<Window.Resources>
or
<UserControl.Resources>
<Style TargetType="DataGrid">
<Style.Resources>
<Style TargetType="Button">
<Setter Property="Background" Value="Red" />
<Setter Property="Margin" Value="0" />
</Style>
</Style.Resources>
</Style>
</UserControl.Resources>

Calendar of DatePicker fills whole screen

I have a DatePicker in my application, that consists of DockPanels in a StackPanel in a ScrollViewer in a UserControl.
The (simplified) xaml of the UserControl looks like this:
<UserControl x:Class="project.UI1"
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"
xml:lang="de-DE"
mc:Ignorable="d" >
<UserControl.Resources>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="Width" Value="250"/>
<Setter Property="TextWrapping" Value="Wrap"/>
<Setter Property="TextAlignment" Value="Right"/>
<Setter Property="VerticalAlignment" Value="Center"/>
<Setter Property="Margin" Value="2"/>
<Setter Property="Padding" Value="3"/>
</Style>
<Style TargetType="{x:Type TextBox}">
<Setter Property="DockPanel.Dock" Value="Top"/>
<Setter Property="TextWrapping" Value="Wrap"/>
<Setter Property="MaxWidth" Value="{Binding RelativeSource={RelativeSource AncestorType=Border},Path=ActualWidth}"/>
<Setter Property="VerticalScrollBarVisibility" Value="Auto"/>
</Style>
<Style TargetType="{x:Type DatePicker}">
<Setter Property="Margin" Value="2"/>
<Setter Property="Width" Value="105"/>
<Setter Property="MaxWidth" Value="105"/>
<Setter Property="Height" Value="24"/>
<Setter Property="VerticalAlignment" Value="Center"/>
<Setter Property="HorizontalAlignment" Value="Left"/>
</Style>
<Style TargetType="{x:Type DockPanel}">
<Setter Property="DockPanel.Dock" Value="Top"/>
</Style>
<Style TargetType="{x:Type Border}">
<Setter Property="Margin" Value="0"/>
<Setter Property="Padding" Value="2"/>
</Style>
<Style TargetType="{x:Type ScrollViewer}">
<Setter Property="HorizontalScrollBarVisibility" Value="Disabled"/>
<Setter Property="VerticalScrollBarVisibility" Value="Auto"/>
</Style>
</UserControl.Resources>
<ScrollViewer>
<StackPanel>
<DockPanel>
<TextBlock Text="IK-Nummer des Absenders (z.B. D-Arzt)"/>
<Border>
<TextBox Text="{Binding p_1}"/>
</Border>
</DockPanel>
<DockPanel>
<TextBlock Text="IK-Nummer der UNI-DAV aus UV-Träger-Verzeichnis"/>
<Border>
<TextBox Text="{Binding p_2}" />
</Border>
</DockPanel>
<DockPanel>
<TextBlock Text="Datum der Erstellung durch den Leistungserbringer"/>
<DatePicker SelectedDate="{Binding p_3}"/>
</DockPanel>
</StackPanel>
</ScrollViewer>
</UserControl>
The TextBlocks have a 250px fixed width and hold the description of the fields while the TextBoxes for the user input are supposed to grow & shrink dynamically as the user resizes the window, to fit the rest of the window width.This is why I came up with packing every TextBlock/TextBox-combo in a DockPanel, and stack those in a StackPanel.
However, when I click on the DatePicker, the calendar beyond spans across the whole screen:
Even though this looks quite funky, I would prefer to get the common square calendar "popup" back.
Unfortunately, I don't know what causes the calendar to go wild like this at the moment...

The problem is your TextBlock style. It is being applied to the DateTimePicker because it has no key and so applies to all TextBlocks down the visual tree.
Can you give the style a key and only apply it to certain TextBlocks?
<Style TargetType="{x:Type TextBlock}" x:Key="TextBlockStyle">
<Setter Property="Width" Value="250"/>
<Setter Property="TextWrapping" Value="Wrap"/>
<Setter Property="TextAlignment" Value="Right"/>
<Setter Property="VerticalAlignment" Value="Center"/>
<Setter Property="Margin" Value="2"/>
<Setter Property="Padding" Value="3"/>
</Style>
....
<TextBlock Text="IK-Nummer der UNI-DAV aus UV-Träger-Verzeichnis"
Style="{StaticResource TextBlockStyle}"/>
UPDATE:
OR, you could just add a new TextBlock style to the DatePicker's resource to override the style higher up in the visual tree:
<DatePicker SelectedDate="{Binding p_3}">
<DatePicker.Resources>
<Style TargetType="{x:Type TextBlock}"/>
</DatePicker.Resources>
</DatePicker>

Nested Styles in WPF

I would like to nest Styles in WPF.
I have a resource dictionary:
<Style x:Key="BottomButtonBar" TargetType="{x:Type Grid}">
<Style TargetType="{x:Type Button}">
<Setter Property="Margin" Value="10,2" />
<Setter Property="Width" Value="90" />
</Style>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="HorizontalAlignment" Value="Center" />
<Setter Property="VerticalAlignment" Value="Center" />
<Setter Property="Margin" Value="2,0"/>
</Style>
</Style>
What I want is: If I apply the style "BottomButtonBar" on a grid, Buttons which are inside this grid have Margin and Width I've defined and the same for the TextBlock inside this grid.
How to do that?

I finally found the following solution:
<Style x:Key="BottomButtonBar" TargetType="{x:Type Grid}">
<Style.Resources>
<Style TargetType="{x:Type Button}">
<Setter Property="Margin" Value="10,2" />
<Setter Property="Width" Value="90" />
</Style>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="HorizontalAlignment" Value="Center" />
<Setter Property="VerticalAlignment" Value="Center" />
<Setter Property="Margin" Value="2,0"/>
</Style>
</Style.Resources>
</Style>
And in the XAML:
<Grid DockPanel.Dock="Bottom" Style="{DynamicResource BottomButtonBar}">

If you want to add styles to elements in the Grid, you can make the styles implicit and add them to the resources of the Grid to limit their scope:
<Grid>
<Grid.Resources>
<Style TargetType="{x:Type Button}">
<Setter Property="Margin" Value="10,2" />
<Setter Property="Width" Value="90" />
</Style>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="HorizontalAlignment" Value="Center" />
<Setter Property="VerticalAlignment" Value="Center" />
<Setter Property="Margin" Value="2,0"/>
</Style>
<Grid.Resources />
<Button ... />
</Grid>