Disable/Enable WPF contextmenu item programmatically

Question

How to modify a specific ContextMenu MenuItem programmatically when the ContextMenu has a Separator in it?

In the parent control I have

ContextMenuOpening="ModifyItems"

The ContextMenu is

<ContextMenu >
    <MenuItem Header="Item1" Tag="SomeTag" />
    <Separator />
    <MenuItem Header="Item2" />                                                     
</ContextMenu>

I handle the ContextMenuOpening (according to Microsoft example)

Private Sub ModifyItems(ByVal sender As System.Object, ByVal e As System.Windows.Controls.ContextMenuEventArgs)
        Dim fe As FrameworkElement = TryCast(e.Source, FrameworkElement)
        Dim cm As ContextMenu = fe.ContextMenu
        For Each mi As MenuItem In cm.Items
            If CType(mi.Tag, String) = "SomeTag" Then
                mi.IsEnabled = IsEnabled()
            End If
        Next mi
End Sub

I run into exception:

Unable to cast object of type 'System.Windows.Controls.Separator' to type 'System.Windows.Controls.MenuItem'.

How to resolve that?

Answer 1

You need to check if the item is a MenuItem:

For Each i In cm.Items
    If TypeOf i Is MenuItem Then
        Dim mi = CType(i, MenuItem)
        If CType(mi.Tag, String) = "SomeTag" Then
            mi.IsEnabled = IsEnabled()
        End If
    End If
Next mi