AutoCAD .NET API基础 > 访问对象的层次结构 > 
引用对象层次结构中的对象
 
 

当使用.NET API中的对象时，用户可以直接或通过自己定义的变量来引用某些对象。要直接引用对象，请将对象包含在调用层次结构中。例如，下列语句附加一个图形文件到当前图形的 Database 中。请注意，层次结构开始于 Application 然后转到 Database 对象。最后从 Database 对象调用 AttachXref 方法：

VB.NET 

Dim strFName As String, strBlkName As String
Dim objId As Autodesk.AutoCAD.DatabaseServices.ObjectId
 
strFName = "c:\clients\Proj 123\grid.dwg"
strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName)
 
objId = Application.DocumentManager.MdiActiveDocument.Database.AttachXref(strFName, strBlkName)

C# 

string strFName, strBlkName;
Autodesk.AutoCAD.DatabaseServices.ObjectId objId;
 
strFName = "c:/clients/Proj 123/grid.dwg";
strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName);
 
objId = Application.DocumentManager.MdiActiveDocument.Database.AttachXref(strFName, strBlkName);

要通过用户定义的变量引用对象，请首先将变量定义为所需类型，然后设置为相应的对象。例如，以下代码定义类型为 Autodesk.AutoCAD.DatabaseServices.Database 的变量 (acCurDb) 并将其设置为等于当前的database：

VB.NET 

Dim acCurDb As Autodesk.AutoCAD.DatabaseServices.Database
acCurDb = Application.DocumentManager.MdiActiveDocument.Database

C# 

Autodesk.AutoCAD.DatabaseServices.Database acCurDb;
acCurDb = Application.DocumentManager.MdiActiveDocument.Database;

以下语句利用acCurDb用户定义的变量附加一个图形文件到 Database中：

VB.NET 

Dim strFName As String, strBlkName As String
Dim objId As Autodesk.AutoCAD.DatabaseServices.ObjectId
 
strFName = "c:\clients\Proj 123\grid.dwg"
strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName)
 
objId = acCurDb.AttachXref(strFName, strBlkName)

C# 

string strFName, strBlkName;
Autodesk.AutoCAD.DatabaseServices.ObjectId objId;
 
strFName = "c:/clients/Proj 123/grid.dwg";
strBlkName = System.IO.Path.GetFileNameWithoutExtension(strFName);
 
objId = acCurDb.AttachXref(strFName, strBlkName);

从模型空间获取图元

本例返回模型空间中的第一个图元对象，类似的代码还可以用来检索图纸空间中的第一个图元。注意：可以将所有的图形对象定义为 Entity 对象：

VB.NET 

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
 
<CommandMethod("ListEntities")> _
Public Sub ListEntities()
  '' 获得当前图形和数据库，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()
      '' 以只读方式打开块表记录   Open the Block table record for read
      Dim acBlkTbl As BlockTable
      acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, _
                                   OpenMode.ForRead)
 
      '' 以只读方式打开模型空间的块表记录    Open the Block table record Model space for read
      Dim acBlkTblRec As BlockTableRecord
      acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace), _
                                      OpenMode.ForRead)
 
      Dim nCnt As Integer = 0
      acDoc.Editor.WriteMessage(vbLf & "Model space objects: ")
 
      ''循环模型空间的每一个对象并显示找到的对象的类型   Step through each object in Model space and
      '' display the type of object found
      For Each acObjId As ObjectId In acBlkTblRec
          acDoc.Editor.WriteMessage(vbLf & acObjId.ObjectClass().DxfName)
 
          nCnt = nCnt + 1
      Next
 
      ''如果没有找到对象就显示下面的信息  If no objects are found then display the following message
      If nCnt = 0 Then
          acDoc.Editor.WriteMessage(vbLf & "  No objects found")
      End If
 
      ''处理事务  Dispose of the transaction
  End Using
End Sub

C# 

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
 
[CommandMethod("ListEntities")]
public static void ListEntities()
{
  // 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())
  {
      // 以只读方式打开块表记录   Open the Block table record for read
      BlockTable acBlkTbl;
      acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
                                   OpenMode.ForRead) as BlockTable;
 
      // 以只读方式打开模型空间的块表记录    Open the Block table record Model space for read
      BlockTableRecord acBlkTblRec;
      acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
                                      OpenMode.ForRead) as BlockTableRecord;
 
      int nCnt = 0;
      acDoc.Editor.WriteMessage("\nModel space objects: ");
 
      // Step through each object in Model space and
      // display the type of object found
      foreach (ObjectId acObjId in acBlkTblRec)
      {
          acDoc.Editor.WriteMessage("\n" + acObjId.ObjectClass.DxfName);
 
          nCnt = nCnt + 1;
      }
 
      // If no objects are found then display a message
      if (nCnt == 0)
      {
          acDoc.Editor.WriteMessage("\n No objects found");
      }
 
      // Dispose of the transaction
  }
}
VBA/ActiveX 代码参考