ContextMenu on TreeView-Element in MVVM-style - wpf

Question

I have the "simple" task to have a ContextMenu on a TreeView(Element) that is done in MVVM-way.
When searching the web I found some solutions that I could bring to work with buttons etc. but not with the TreeView. I think the problem is with setting the ItemsSource-Property of TreeView that gives every single item an own DataContext.
Here's my little Test-App where you can see the principle working for button but not for the TreeView-Elements:
MainWindow.xaml:
<Window x:Class="ContextMenu.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid >
<StackPanel>
<TextBlock Text="{Binding MyText}" />
<Button Tag="{Binding DataContext,RelativeSource={RelativeSource Mode=Self}}" Content="Click me">
<Button.ContextMenu>
<ContextMenu>
<MenuItem Header="{Binding PlacementTarget.Tag.MyText,
RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ContextMenu}}" />
</ContextMenu>
</Button.ContextMenu>
</Button>
<TreeView ItemsSource="{Binding MyList}" Tag="{Binding DataContext, RelativeSource={RelativeSource Mode=Self}}">
<TreeView.ItemTemplate>
<HierarchicalDataTemplate>
<TextBlock Text="{Binding Name}">
<TextBlock.ContextMenu>
<ContextMenu>
<MenuItem Header="{Binding Path=PlacementTarget.Tag.MyText,
RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ContextMenu}}" />
</ContextMenu>
</TextBlock.ContextMenu>
</TextBlock>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
</StackPanel>
</Grid>
</Window>
Codebehind:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
DataContext = new MainWindowVM();
}
}
MainWindowVM.cs:
public class MainWindowVM
{
public string MyText { get; set; }
public ObservableCollection<TreeElement> MyList { get; set; }
public MainWindowVM()
{
MyText = "This is my Text!";
MyList = new ObservableCollection<TreeElement>();
MyList.Add(new TreeElement("String 1"));
MyList.Add(new TreeElement("String 2"));
}
}
public class TreeElement
{
public string Name { get; set; }
public TreeElement(string Name)
{
this.Name = Name;
}
}
Thanks for your help!!
Joerg

Answer 1

You are close.
What you are doing:
you set the Tag of TreeView to its own DataContext. This is
unnecessary.
you try to get Tag.MyText from your ContextMenu.PlacementTarget - which is TextBlock. The TextBlock has no Tag set.
What you should do:
set the Tag of the TextBlock to DataContext of the Window
(Window is TextBlock ancestor and you should look it up via
RelativeSource Mode=FindAncestor).
the second part is OK - you have TextBlock.Tag set in the first step.