Windows Phone Toolkit Context Menu Items have wrong object bound to them when an item is removed and then added

Question

I just encountered a serious problem with Context Menu which I cannot resolve for hours.

To reproduce the problem I created a brand new Panorama app with the app templates for Windows Phone 8 in Visual Studio 2012. I installed Windows Phone toolkit via nugget and add context menu in the data template of the first long list selector which is bound to Items

<StackPanel Margin="0,-6,0,12">
    <TextBlock Text="{Binding LineOne}" TextWrapping="Wrap" Style="{StaticResource PhoneTextExtraLargeStyle}" FontSize="{StaticResource PhoneFontSizeExtraLarge}"/>
    <toolkit:ContextMenuService.ContextMenu>
        <toolkit:ContextMenu>
            <toolkit:MenuItem Header="{Binding LineOne}" Click="MenuItem_Click_1" Tag="{Binding}">
            </toolkit:MenuItem>
        </toolkit:ContextMenu>
    </toolkit:ContextMenuService.ContextMenu>
</StackPanel>

I set the header to the LineOne property for easier debugging. I attached the following event:

private void MenuItem_Click_1(object sender, RoutedEventArgs e)
{
    var itemViewModel = (ItemViewModel)((MenuItem)sender).Tag;
    App.ViewModel.Items.Remove(itemViewModel);
    App.ViewModel.Items.Add(new ItemViewModel { LineOne = "Test", LineTwo = "Test", LineThree = "Test" });
}

I run the app and use the context menu to remove the first item. The first item disappears and a new item named Test appears at the bottom of the list as expected. If I hold this new item the menu item is bound to "runtime one" (the item that was deleted).

This was the simplest code I could get to reproduce the error but in my real app I have pretty much the same problem with more meaningful code for adding and deleting in different methods and even different pages. I had a command bound but since the databinding is wrong the command is run in the wrong view model with the wrong parameter.

Any idea why this is happening?

Answer 1

For those like me not wanting to recompile toolkit here is an easy workaround based on pantaloons answer. Simpy add Opened event handler:

<toolkit:ContextMenu Opened="ContextMenu_Opened">
...
</toolkit:ContextMenu>

Event Handler code:

private void ContextMenu_Opened(object sender, RoutedEventArgs e)
{
    var menu = (ContextMenu)sender;
    var owner = (FrameworkElement)menu.Owner;
    if (owner.DataContext != menu.DataContext)
        menu.DataContext = owner.DataContext;

}