右键单击后，禁用的上下文菜单不会消失

Question

I have a ContextMenu as part of a TabControl such as:

<TabControl Name="MyTabControl">
    <TabControl.ContextMenu>
        <ContextMenu Name="MyContextMenu" IsEnabled="False" StaysOpen="True">
            <MenuItem Header="Item1"></MenuItem>
            ...
        </ContextMenu>
    </TabControl.ContextMenu>
</TabControl>

As you can see, the menu is disabled. It will be enabled later in the program, for now however, it should remain in its disabled state. The problem is, when I right-click the TabControl and the disabled menu shows, it simply stays where it was first opened, no other right-click will move it, nor will a left-click somewhere make it disappear.

The only way to get rid of it, would be either by enabling it and then right/left-clicking, or by using MyContextMenu.Visibility = Visibility.Collapsed/Hidden;

I tried setting the StaysOpen -property to False . Then the menu will open once in its disabled state. After left-clicking disappear and then not appear again even if it gets enabled.

The only way around it could be changing the StaysOpen -property along with the IsEnabled -property, but it is a bit weird that the menu opens exactly once in its disabled state and then not anymore.

I hope anybody could explain to me, why exactly a disabled menu won't close and the property StaysOpen at false makes it open exactly once, because it seems like a weird behaviour to me.

Answer 1

It seems that the behaviour of context menu items is quite strange - what you've described is in .Net 4.0 and if you target yor app to .Net 3.5 for instance you will notice the opposite behaviour - you can't make the menu stay opened if the single item is disabled, it just disappears immediately after it shows on right click.

However I think the preferrable way to manage the enabled state of a context menu item (and also the OnClick action it should do) is by a Command .

First you should specify a datacontext for your view, let's say it is the class ViewModel.cs . Then create a command by implementing the ICommand interface, something like this:

public class MyCommand : ICommand

And then you have a CanExecute method which does exactly what it's name says - decides if the command can be executed or not. And the enabled state of the menu item also depends on the return value of this method. So you can keep it returning false as long as you need in and the menu will behave correctly and the menu item will be disabled. Then when you want you can make it return true (by some logic in the method itself) and you'll have again a properly working context menu with enabled menu item.

If you want to disable the entire menu, use the same approach but for the menu.

And if you need to make all the items in the menu disabled (which I think is different from the entire menu), then you can use something like this:

<TabControl Name="MyTabControl" Background="Green">
            <TabControl.ContextMenu>
                <ContextMenu Name="MyContextMenu"  StaysOpen="True" ItemsSource="{Binding  Items}">
                    <ContextMenu.ItemTemplate>
                        <DataTemplate >
                            <MenuItem Header="{Binding Header}"  IsEnabled="False" />
                        </DataTemplate>
                    </ContextMenu.ItemTemplate>
                </ContextMenu>
            </TabControl.ContextMenu>
        </TabControl> 

Here your ItemsSource ( Items ) is for instance List<MenuItem> , and MenuItem itselw would be your Model (thinking in MVVM) for each of your menu items, which should have property Header that contains the header you want to see in each menu item. Instead of setting the IsEnabled to false as in my dummy example, you can bind it to a property in order to have control on when it must be true and false.