VB.NET 获取 AutoCAD 中 Polyline2d 顶点数量

在 VB.NET 中，可以使用以下代码来显示 Polyline2d 类型的数据元素个数：

Dim acDoc As Document = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument
Dim acCurDb As Database = acDoc.Database
Dim acEd As Editor = acDoc.Editor

Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
    Dim acBlkTbl As BlockTable = acTrans.GetObject(acCurDb.BlockTableId, OpenMode.ForRead)
    Dim acBlkTblRec As BlockTableRecord = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), OpenMode.ForRead)

    For Each acObjId As ObjectId In acBlkTblRec
        Dim acEnt As Entity = acTrans.GetObject(acObjId, OpenMode.ForRead)

        If TypeOf acEnt Is Polyline2d Then
            Dim acPoly2d As Polyline2d = DirectCast(acEnt, Polyline2d)
            acEd.WriteMessage('Polyline2d contains ' & acPoly2d.NumberOfVertices & ' vertices.')
        End If
    Next
    acTrans.Commit()
End Using

这段代码首先获取当前活动文档的数据库和编辑器对象。然后通过事务来访问模型空间的块表记录。接着遍历块表记录中的每个实体，如果实体是 Polyline2d 类型，则将其转换成 Polyline2d 对象，并使用 NumberOfVertices 属性来获取顶点的个数，并使用编辑器对象的 WriteMessage 方法来显示顶点的个数。最后提交事务以结束操作。