Hi He Ying,
The click on the submenu header is used for opening another submenu. When you set a delay for the opening of the popup , the click on the header will still open it immediately despite the delay setting. So you cannot use the click on the header for other implementation purposes like closing the menu.
If you intend to use the desired functionality for marking a user's choice like selection among a variety of options, you might want to consider using checkable menu items
. The menu items will be checkable if you set IsCheckable="True".
I hope this helps.
the Telerik team
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