I wanted to use the grouping feature.
Sometimes my group is "big" so it takes time to expand it.
So I wanted to add
-a busyIndicator.IsBusy = true in the GroupRowIsExpandedChanging handler
-a busyIndicator.IsBusy = false in the GroupRowIsExpandedChanged handler
However, the GroupRowIsExpandedChanging is never raised, only GroupRowIsExpandedChanged occured.
I'm using 2010.3.1407.1040.