From a given MetadataWorkspace, let's call mw, i use this:
var cSpaceEntities = mw.GetItems(DataSpace.CSpace).OfType<EntityType>();
foreach (var entity in cSpaceEntities) {
var autoIds = entity.KeyMembers.Where(p =>
p.MetadataProperties
.Any(m => m.PropertyKind == PropertyKind.Extended
&& Convert.ToString(m.Value) == "Identity")).ToArray();
}
please test