WPF：将背景保留在边框中

Question

I have a treeview with items that can be colored differently. Like this

As you can see the background is bigger than the border. How can I keep the background color inside the border?

This is the relevant code:

<DataTemplate DataType="{x:Type models:MyClass}">
    <Border BorderBrush="Black" 
            HorizontalAlignment="Stretch" 
            BorderThickness="1" 
            Margin="2" >                
        <TextBlock Text="{Binding Path=Name}" 
                   Foreground="Black" 
                   Width="{Binding Path=ActualWidth, ElementName=MyTreeView, Mode=OneWay}" 
                   Background="{Binding Background}" 
                   Margin="3" />
    </Border>
</DataTemplate>

Answer 1

To set the background I use a property in my TextBlock

Background="{Binding Background}" 

In my ViewModel I set the background of the TreeViewItem like this

var item = new TreeViewItem { Header = myClassInstance };
item.Background = Brushes.Blue;

which led to the problematic overlapping background color.

I changed it to set the background not to the TreeViewItem but to my class instance in the item. So I changed the above 2 lines to

var item = new TreeViewItem { Header = myClassInstance };
myClassInstance.Background = Brushes.Blue;

and it works as expected.