怎样创建一个新块？

cq_starsea

我要创建一个新块，块里面只有一个圆，我的代码如下，但是没创建起，请大家帮忙看看。谢谢！
    <CommandMethod("A2")>
    Public Sub A2()
        Dim doc As Autodesk.AutoCAD.ApplicationServices.Document = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument
        Dim db As Database = doc.Database
        Dim blockName As String = "asdsadsa"
        Using trans As Transaction = db.TransactionManager.StartTransaction
            Dim ModelSpace As BlockTableRecord = trans.GetObject(db.CurrentSpaceId, OpenMode.ForWrite)

            Dim bt As BlockTable = trans.GetObject(db.BlockTableId, OpenMode.ForWrite)
            Dim btr As BlockTableRecord = New BlockTableRecord()

            If Not bt.Has(blockName) Then
                btr.Name = blockName

                Dim clr As New Circle
                clr.Center = New Point3d(100, 100, 0)
                clr.Radius = 40
                ModelSpace.AppendEntity(clr)

                bt.UpgradeOpen()
                bt.Add(btr)
                trans.AddNewlyCreatedDBObject(btr, True)

                bt.DowngradeOpen()
            End If
            trans.Commit()
        End Using
    End Sub

sieben

ModelSpace.AppendEntity(clr)

改为 btr.AppendEntity(clr)

sieben

另外还要有 trans.AddNewlyCreatedDBObject(cir, True)