如何使用反射从自定义控件中删除单击事件？

Question

I have a custom control (MenuButton) in WPF that subscribes to a Click event. I now want to use reflection to unsubscribe from the event. This is what my code currently looks like:

private void RemoveClickEvent(MenuButton mbButton)
{
    FieldInfo fiFieldInfo = mbButton.GetType().GetField("Click", BindingFlags.Public | BindingFlags.NonPublic |
                                                        BindingFlags.Instance |BindingFlags.Static | BindingFlags.GetField);
    object objValue = fiFieldInfo.GetValue(mbButton);
    PropertyInfo piProprtyInfo = mbButton.GetType().GetProperty("Events", BindingFlags.Public | BindingFlags.NonPublic |
                                                                BindingFlags.Instance | BindingFlags.Static | BindingFlags.GetField | BindingFlags.GetProperty);

    EventHandlerList ehEventHandlers = (EventHandlerList)piProprtyInfo.GetValue(mbButton, null);
    ehEventHandlers.RemoveHandler(objValue, ehEventHandlers[objValue]);
}

I can successfully get the FieldInfo object, but the PropertyInfo object comes out as null. How do I fix my code so that the method works properly? For the record, I am targeting .NET Framework 4.

Edit:

Here is how I subscribe to the events.

private void PageStart()
{
    //Subscribe to the necessary event when a page is first loaded
    foreach (MenuButton mbItem in mbMenuButtonsList)
    {
        if (mbItem.HideExtraInfo == true)
        {
            mbButton.Click += (sender, e) => ShowOrHideControls(sender, e, true);
        }
        else
        {
            mbButton.Click += (sender, e) => ShowOrHideControls(sender, e, false);
        }
    }
}

private void PageEnd()
{
    //When moving to the next page, unsubscribe from the events
    foreach (MenuButton mbItem in mbMenuButtonsList)
    {
        RemoveClickEvent(mbItem);
    }
}

Edit #2:

Something I neglected to mention, some of the events I use in my project also require the MenuButton to be passed in, like so:

UIElementCollection ctrlControls = MainCanvas.Children;
mbButton.Click += (sender, e) => ChangeControls(sender, e, mbButton, ctrlControls, false);

How do I work around this if I stop using Lambda expressions?

Answer 1

If instead of using lambdas to subscribe to your events, you use methods, unsubscribing is easy:

if (mbItem.HideExtraInfo == true)
{
    mbButton.Click += ShowControls;
}
else
{
    mbButton.Click += HideControls;
}

private void ShowControls(object sender, EventArgs e) => ShowOrHideControls(sender, e, true);
private void HideControls(object sender, EventArgs e) => ShowOrHideControls(sender, e, false);

private void PageEnd()
{
    //When moving to the next page, unsubscribe from the events
    foreach (MenuButton mbItem in mbMenuButtonsList)
    {
        mbItem.Click -= ShowControls;
        mbItem.Click -= HideControls;
    }
}

Answer 2

That's pretty easy to handle, don't use lambda expressions!

private void PageStart()
{
    //Subscribe to the necessary event when a page is first loaded
    foreach (MenuButton mbItem in mbMenuButtonsList)
    {
        if (mbItem.HideExtraInfo == true)
        {
            mbButton.Click += true_handler;
        }
        else
        {
            mbButton.Click += false_handler;
        }
    }
}

void true_handler(object sender, EventArgs args)
{
    ShowOrHideControls(sender, e, true);
}

void false_handler(object sender, EventArgs args)
{
    ShowOrHideControls(sender, e, false);
}

private void PageEnd()
{
    //When moving to the next page, unsubscribe from the events
    foreach (MenuButton mbItem in mbMenuButtonsList)
    {
        if (mbItem.HideExtraInfo == true)
        {
            mbButton.Click -= true_handler;
        }
        else
        {
            mbButton.Click -= false_handler;
        }
    }
}