Commented Unassigned: Dropdownbutton unexpected IsOpen behaviour [22229]

When you bind IsOpen to a viewmodel property, the DropDownButton control seems to only read the IsOpen value once when the control is created, setting it's initial state. After that, the bound property is never updated or read again as you open and close the popup (or when you modify the viewmodel property). From the description this appears to be incorrect behavior. Has anyone else experienced this?
Comments: ** Comment from web user: curiousKoala **

Interesting, I noticed you had to set the DataContext for this control explicitly. Most controls I have worked with you don't have to do that. I will investigate and post results.