wpf weird MenuItem visibility issue

Question

I have simple scenario in which i hide and show a signle MenuItem in a contextmenu as shown below:

Xaml:

<Window x:Class="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.ContextMenu>
    <ContextMenu Name="mainMnu">
        <MenuItem Name="mnu" Header="Testing"/>
    </ContextMenu>
</Window.ContextMenu>

<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
    <Button HorizontalAlignment="Left" Margin="52,131,0,108" Name="Button1" Width="75">Button</Button>
</Grid>

code behind:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles Button1.Click
    If mnu.Visibility = Windows.Visibility.Visible Then
        mnu.Visibility = Windows.Visibility.Collapsed
        mainMnu.Visibility = Windows.Visibility.Collapsed
    Else
        mnu.Visibility = Windows.Visibility.Visible
        mainMnu.Visibility = Windows.Visibility.Visible
    End If

End Sub

The Problem is that every other time i press the button the menuitem is not shown. Right click only shows a small empty rectangle. (like there is a visible menu, but not a visible menuitem). It somehow works in a cycle... first 2 clicks: problem, next 2 clicks ok, and so on...

Any ideas?

Answer 1

If you're trying to disable the context menu, setting its Visibility is the wrong way to do it.

Instead, you should set the ContextMenu property to Nothing.

For example:

If ContextMenu Is Nothing Then
    ContextMenu = mainMnu
Else
    ContextMenu = Nothing
End If