Tạo Đường Tròn trong AutoCAD bằng VB.Net

Public Sub AddCircle(ByVal X, ByVal Y, ByVal R)
        '' Get the current document and database
        Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
        Dim acCurDb As Database = acDoc.Database
        '' Start a transaction
        Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()

            '' Open the Block table for read
            Dim acBlkTbl As BlockTable
            acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, DatabaseServices.OpenMode.ForRead)
            '' Open the Block table record Model space for write
            Dim acBlkTblRec As BlockTableRecord
            acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), DatabaseServices.OpenMode.ForWrite)
            Dim DT As Circle = New Circle()
            DT.SetDatabaseDefaults()
            DT.Center = New Point3d(X, Y, 0)
            DT.Radius = R
            '' Add the new object to the block table record and the transaction
            acBlkTblRec.AppendEntity(DT)
            acTrans.AddNewlyCreatedDBObject(DT, True)
            '' Save the new object to the database
            acTrans.Commit()
        End Using
    End Sub