Thank you on your suggestion, but unfortunately this did not help in our specific problem.
RadDropDown button was still not closed and CommitEdit action was not performed.
Finally we solved it by adding a bit of a hack code to GetNewValueFromEditor methods in our custom column class:
//close dropdown button
(editor as RadDropDownButton).IsOpen = false;
//focus parent grid of control
RadGridView parentGrid = (editor as RadDropDownButton).ParentOfType<
We force RadDropDown button to close and return focus to parent RadGridView.
And now CommitEdit action will be performed when user clicks button in menu...
I know it is not very elegant, but it worked. :)