public void SetContext(Guid contextId, bool activate)
{
uint cookie;
var monitorSelection = (IVsMonitorSelection)this;
Assert.IsTrue(ErrorHandler.Succeeded(monitorSelection.GetCmdUIContextCookie(ref contextId, out cookie)));
Assert.IsTrue(ErrorHandler.Succeeded(monitorSelection.SetCmdUIContext(cookie, activate ? 1 : 0)));
}