How to add additional actions to command

Question

I am inheriting from a window control that already handles the ApplicationCommands.Close command so that it handles closing the window natively.

I would like to add/override the existing functionality, however I cannot seem to figure out how to do this.

Tried:

Adding another of the same command to CommandBindings (first declared seems to win)
Check if the command is already existing...Cannot seem to find a way to do this

score 1 · Answer 1 · answered Jun 25 '13 at 19:44

1

There are a couple of things you can try. If you are just trying to prevent your window from closing, you can override the OnClosing method and set the cancelled flag:

protected override void OnClosing(CancelEventArgs e)
{
    e.Cancel = true;
    base.OnClosing(e);
}

If you want to specifically alter the behavior, you can register with preview versions of the command:

<Window.CommandBindings>
    <CommandBinding Command="ApplicationCommands.Close"
                    PreviewExecuted="CloseCommandHandler"
                    PreviewCanExecute="CanExecuteHandler" />
</Window.CommandBindings>

The preview routed events will happen before the standard events, allowing you to handle the logic before your base class.

answered Jun 25 '13 at 19:44

Abe Heidebrecht

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Yah, I am indeed trying that and figured I might have to go with the Closing event. I can't use preview because of this bug http://stackoverflow.com/questions/2281825/routeduicommand-previewexecuted-bug I feel like this problem could crop up again, so I am going to leave it open in the hopes for an answer to my actual question. Still +1 – Justin Pihony Jun 25 '13 at 20:17
That seems like a nasty bug. I just cracked it open in reflector, and in .NET 4.5 at least, unless you set e.Handled = true in the preview event handler, the normal handler will still get called. So, depending on the version of .NET you're on, this may work! – Abe Heidebrecht Jun 26 '13 at 13:43

score 0 · Answer 2 · answered Jun 25 '13 at 21:52

If you want to replace functionality of the global command, you can find the specific command binding, remove it then add your own logic. See below.

    public ChildWindow()
        :base()
    {
        var appCloseCommandBinding =
            CommandBindings.Cast<CommandBinding>().SingleOrDefault(item => item.Command == ApplicationCommands.Close);

        if(appCloseCommandBinding != null)
            CommandBindings.Remove(appCloseCommandBinding);

        CommandBindings.Add(new CommandBinding(ApplicationCommands.Close, YourCommandLogic));
    }

Hope it can help.

How to add additional actions to command

2 Answers2