public static void ClearAll(UpdateHandler handler)
{
// Take a copy of the list because the items will be deleted from the update handler
// as SetShow() gets called, and .NET won't let you iterate over the collection
// directly while you do that:
List<VectorRenderer> allOfMe = new List<VectorRenderer>();
foreach (VectorRenderer item in handler.GetAllUpdatersOfType(typeof(VectorRenderer)))
allOfMe.Add(item);
// Now actually turn them all off:
foreach (VectorRenderer vecRend in allOfMe)
vecRend.SetShow(false);
}