AutoCAD .NET API基础 > 集合对象 > 
删除集合对象中的成员
 
 

集合的成员可以从集合对象被删除，只要使用成员对象的 Erase 方法。例如，下面的代码从 LayerTable 对象中删除层 MyLayer。

在从图形中删除图层前，应该确定它可以被删除。若要确定一个图层或另外的像块（Block） 或文字样式（TextStyle）可以被删除，应该使用 Purge 方法。关于 Purge 方法的更多信息，请参见 清理未引用的命名对象部分。

VB.NET 

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
 
<CommandMethod("RemoveMyLayer")> _
Public Sub RemoveMyLayer()
  ''获得当前文档和数据库，并启动一个事务   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()
      ''返回当前数据库的层表   Returns the layer table for the current database
      Dim acLyrTbl As LayerTable
      acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId, _
                                   OpenMode.ForRead)
 
      ''检验名字为 MyLayer 的图层是否已经存在在层表中 Check to see if MyLayer exists in the Layer table
      If acLyrTbl.Has("MyLayer") = True Then
          Dim acLyrTblRec As LayerTableRecord
          acLyrTblRec = acTrans.GetObject(acLyrTbl("MyLayer"), _
                                          OpenMode.ForWrite)
 
          Try
              acLyrTblRec.Erase()
              acDoc.Editor.WriteMessage(vbLf & "'MyLayer' was erased")
 
              '' 确认所做的修改  Commit the changes
              acTrans.Commit()
          Catch
              acDoc.Editor.WriteMessage(vbLf & "'MyLayer' could not be erased")
          End Try
      Else
          acDoc.Editor.WriteMessage(vbLf & "'MyLayer' does not exist")
      End If
 
      '' 销毁事务  Dispose of the transaction
  End Using
End Sub

C# 

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
 
[CommandMethod("RemoveMyLayer")]
public static void RemoveMyLayer()
{
  // Get the current document and database, and start a transaction
  Document acDoc = Application.DocumentManager.MdiActiveDocument;
  Database acCurDb = acDoc.Database;
 
  using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
  {
      // Returns the layer table for the current database
      LayerTable acLyrTbl;
      acLyrTbl = acTrans.GetObject(acCurDb.LayerTableId,
                                   OpenMode.ForRead) as LayerTable;
 
      // Check to see if MyLayer exists in the Layer table
      if (acLyrTbl.Has("MyLayer") == true)
      {
          LayerTableRecord acLyrTblRec;
          acLyrTblRec = acTrans.GetObject(acLyrTbl["MyLayer"],
                                          OpenMode.ForWrite) as LayerTableRecord;
 
          try
          {
              acLyrTblRec.Erase();
              acDoc.Editor.WriteMessage("\n'MyLayer' was erased");
 
              // Commit the changes
              acTrans.Commit();
          }
          catch
          {
              acDoc.Editor.WriteMessage("\n'MyLayer' could not be erased");
          }
      }
      else
      {
          acDoc.Editor.WriteMessage("\n'MyLayer' does not exist");
      }
 
      // Dispose of the transaction
  }
}
VBA/ActiveX 代码参考

一旦对象被删除，就不应该在程序后面的部分尝试访问这个对象；否则将会产生错误。上面的例子测试一个对象在再次被访问前是否存在。当需要删除一个对象时，应该使用 Has 方法或 Try Catch 语句捕捉任何出现的异常以检查对象是否存在。更多关于处理异常的信息，请参见 处理错误部分。