Autocad API，读取块属性铸造错误

Question

我收到以下错误

"Unable to cast object of type
autodesk.autocad.databaseservices.polyline to type autodesk.autocad.databaseservices.blockrefereance

在读取方块属性时绘图上有很多东西。

代码：

Dim db As Database = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Database

Using tr As Transaction = db.TransactionManager.StartTransaction

Dim ed As Editor = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument.Editor
Dim blockids As ObjectIdCollection = New ObjectIdCollection
Dim bt As BlockTable = tr.GetObject(db.BlockTableId, OpenMode.ForRead)
Dim btr As BlockTableRecord = tr.GetObject(bt(BlockTableRecord.ModelSpace), OpenMode.ForRead)

For Each objid As ObjectId In btr

    If btr.IsAnonymous = False Or btr.IsLayout = False Then

        Dim blkref As BlockReference = tr.GetObject(objid, OpenMode.ForRead)

        Dim attcol As AttributeCollection = blkref.AttributeCollection

        For Each attid As ObjectId In attcol

            Dim attref As AttributeReference = tr.GetObject(attid, OpenMode.ForRead)

            ed.WriteMessage(attref.Tag.ToString & vbNewLine)

            ed.WriteMessage(attref.TextString.ToString & vbNewLine)

        Next

    End If

Next

tr.Commit()

End Using

你能帮忙吗！！！

Answer 1

您的代码在 btr (ModelSpace) 中循环，但假设它只处理块。

您需要先进行另一次检查，以确认您正在检查的实体类型。最好在检查它是否是匿名之前。

Answer 2

问题是什么？

我有一个装满各种 goods/products 的购物篮。牛奶、小苏打、苹果。香蕉。有些东西可以吃，有些东西有毒。如果我假设所有的东西都是可食用的并且我尝试吃一些东西——那可能会导致一些非常严重的问题。例如我可以吃苹果，但如果我尝试吃牙刷，那么我的 body 就会崩溃并抛出错误。一定要先确认能不能吃再放进嘴里…………啊，好吧，我们继续……Autocad也是一样。

解决方案很简单：首先检查您正在处理的 object 是否是 blockReference。如果是这样，那么继续。我没有检查下面的代码，因为我不是 VB.NET 专家，但是像这样的东西可以让你在继续之前检查你是否正在处理 blockReference：

For Each objid As ObjectId In btr

If btr.IsAnonymous = False Or btr.IsLayout = False Then

  Dim ent as Entity = tr.GetObject(objid, OpenMode.ForRead)  // ADD THIS LINE

  If TypeOf ent Is [BlockReference] Then            // ADD THIS IF STATEMENT


             // ADD IN THE REST OF YOUR CODE HERE 
             // e.g.  Dim blkref As BlockReference = tr.GetObject(objid, 
             //  OpenMode.ForRead) etc.



  End If

Autocad API，读取块属性铸造错误

Autocad API , reading block attributes casting error

vb.net

autocad-plugin