How to dispose dynamic menu items???

[andylotus]

Hi People

I have a WinForm program. The UI contains a ToolStripDropdownButton,
which is associate a list of menu items of ToolStripMenuItem, created
dynamically. Upon different scenarios of user operations, the
DropdowButton need to clean up all its menuitems, and create new ones.

Here the codes:
////////////////////
Void CreateForEmail()
{
....
button.DropDownItems.Clear();
....
button.DropDownItems.Add("To:", null, HandleOutlookToClick);
button.DropDownItems.Add("CC:", null, HandleOutlookCCClick);
}

Void CreateForPhone()
{
....
button.DropDownItems.Clear();
....
button.DropDownItems.Add("Phone", null, HandlePhoneClick);

}

Void CreateForNone()
{
button.DropDownItems.Clear();
}
////////////////////////
So far so good, just work as I expect.
Later on, I found out that " button.DropDownItems.Clear();" does not
dispose the menu items at all, when I decided to add shortcutkeys to
menu items. The above codes were changed in order to have shortCutKeys:
////////////////////
Void CreateForEmail()
{
....
button.DropDownItems.Clear();
....
button.DropDownItems.Add("To:", null, HandleOutlookToClick)
..ShortcutKeys = Keys.F9;;
button.DropDownItems.Add("CC:", null, HandleOutlookCCClick);
}

Void CreateForPhone()
{
....
button.DropDownItems.Clear();
....
button.DropDownItems.Add("Phone", null, HandlePhoneClick) .ShortcutKeys
= Keys.F9;;

}

Void CreateForNone()
{
button.DropDownItems.Clear();
}
////////////////////////

After CreateForNone is called, and I press F9, either
HandleOutlookToClick or HandlePhoneClick will be called, depending
which one was last called. Obviously, those menu items are still in the
program accepting keyboard shortcut, though they are not invisible.

So I replace "button.DropDownItems.Clear();" with the following
////////////////
private void ClearButtonDropdown()
{
for (int i = Button.DropDownItems.Count - 1; i >= 0; i--)
{
ToolStripMenuItem m = Button.DropDownItems as
ToolStripMenuItem;
Button.DropDownItems.Remove(m);
m.Dispose();
}
Button.DropDownItems.Clear();
// even GC.Collect() will not have effect.
}
///////////////
However, strange things remain the same.
Obviously someone is still holding references to those menu items,
stopping GC from disposing those items.

Can you point out how to dispose these menu items?

Cheers


Andy

 

[John J. Hughes II]

Just a guess, have you tried clearing the shortcut key before deleting the
item?

Regard,
John

 

[Andy Lotus]

Just a guess, have you tried clearing the shortcut key before deleting the
item?

Regard,
John

Thanks John.

Yes, it work fine now. Just before I clear the menu items, I check
every items and assign ShortcutKeys with ShortcutKeys.None.

I think (guess) the shortcuts work this way:
1. Application traps key inputs for hot keys at application level
2. Form traps key inputs for shortcuts at window level.
3. When assigning a shortcut to a menu item, the item is registered
with some kind of Shortcut Manager somewhere.
4. When user presses a shortcut, the shortcut manager will be aware of
it, and trigger the menu item associated with the shortcut.
5. When I call dispose upon the menu item, the Shortcut Manager still
have reference to the item, so GAC can do nothing about it.
6. After I assigned None to the item, apparently this will unregister
the item from the manager.

In addition, I also check the memory usage through Process Manager.
After I created those dynamic menu items, say a few dozens times per
minutes, the memory usage kept stable, obviously those items got
disposed and reused normally. I felt happy every since.