如何在.net开发的代码中遍历所有的图形对象，并判断是什么类型的对象!

Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor
Dim db As Database = Application.DocumentManager.MdiActiveDocument.Database
Using trans As Transaction = db.TransactionManager.StartTransaction()
Dim bt As BlockTable = trans.GetObject(db.BlockTableId, OpenMode.ForRead)
Dim btr As BlockTableRecord = trans.GetObject(bt(BlockTableRecord.ModelSpace), OpenMode.ForRead)
Dim id As ObjectId
For Each id In btr
Dim entity As Entity = trans.GetObject(id, OpenMode.ForRead, True)
ed.WriteMessage(entity.GetType.Name)
Next
trans.Commit()
End Using