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ObjectARX 开发指南

将 VBA 或 VB 中的错误处理程序与 VB.NET （.NET）进行比较

2023-1-1 08:50| 发布者: admin| 查看: 962| 评论: 0|来自: AutoCAD

VBA 或 VB 中的错误处理是使用语句完成的。虽然这些语句可以毫无问题地与 VB.NET 一起使用，但建议改用语句。语句比 AND 语句更灵活。On ErrorOn ErrorTryTryOn Error Resume NextOn Error GoTo Label

可以使用语句重写 and 语句的用法。下面演示如何使用重写语句。On Error Resume NextOn Error GoTo LabelTry-CatchOn Error GoTo LabelTry-Catch

出错时 - VBA

Sub ColorEntities()
    On Error GoTo MyErrorHandler
 
    Dim entry As Object
    For Each entry In ThisDrawing.ModelSpace
        entry.color = acRed
    Next entry
 
    ' Important! Exit the subroutine before the error handler
  Exit Sub
 
MyErrorHandler:
    MsgBox entry.EntityName + " is on a locked layer." + _
                              " The handle is: " + entry.Handle
  Resume Next
End Sub

试捕 - VB.NET

<CommandMethod("ColorEntities")> _
Public Sub ColorEntities()
  '' Get the current document and database, and start a transaction
  Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
  Dim acCurDb As Database = acDoc.Database
 
  Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
      '' Open the Block table record for read
      Dim acBlkTbl As BlockTable
      acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, _
                                   OpenMode.ForRead)
 
      '' Open the Block table record Model space for read
      Dim acBlkTblRec As BlockTableRecord
      acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), _
                                      OpenMode.ForRead)
 
      Dim acObjId As ObjectId
 
      '' Step through each object in Model space
      For Each acObjId In acBlkTblRec
          Try
              Dim acEnt As Entity
              acEnt = acTrans.GetObject(acObjId, _
                                        OpenMode.ForWrite)
 
              acEnt.ColorIndex = 1
          Catch
              Application.ShowAlertDialog(acObjId.ObjectClass.DxfName & _
                                          " is on a locked layer." & _
                                          " The handle is: " & acObjId.Handle.ToString())
          End Try
      Next
 
      acTrans.Commit()
  End Using
End Sub