"Collapse All" button in Solution Explorer

My projects are large and well organized, but I frequently find myself collapsing many nodes in the project tree to get my working state back under control again. Unfortunately, if I add a file or "Refresh" the project, all of the collapsed folders open up again. The only way around the problem is to collapse every folder before closing the project, and then reopening it again.

Could you add a "Collapse All" button to the Solution Explorer?