对象层次结构中的引用对象 （.NET）

在 AutoCAD .NET API 中处理对象时，可以直接引用某些对象，也可以根据正在使用的对象通过用户定义的变量引用某些对象。若要直接引用对象，请将该对象包含在调用层次结构中。例如，以下语句将图形文件附加到当前图形的数据库。请注意，层次结构从应用程序开始，然后转到对象。从对象，该方法称为：DatabaseDatabaseAttachXref

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，请将变量定义为所需类型，然后将变量设置为适当的对象。例如，下面的代码定义一个 type 的变量 （），并将该变量设置为等于当前数据库：acCurDbAutodesk.AutoCAD.DatabaseServices.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;

然后，以下语句使用用户定义的变量将图形文件附着到数据库：acCurDb

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);

从模型空间检索实体

下面的示例返回模型空间中的第一个实体对象。类似的代码可以对图纸空间实体执行相同的操作。请注意，所有图形对象都定义为一个对象：Entity

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
 
<CommandMethod("ListEntities")> _
Public Sub ListEntities()
  '' 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 nCnt As Integer = 0
      acDoc.Editor.WriteMessage(vbLf & "Model space objects: ")
 
      '' 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
 
      '' If no objects are found then display the following message
      If nCnt = 0 Then
          acDoc.Editor.WriteMessage(vbLf & "  No objects found")
      End If
 
      '' Dispose of the transaction
  End Using
End Sub

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())
  {
      // Open the Block table record for read
      BlockTable acBlkTbl;
      acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
                                   OpenMode.ForRead) as BlockTable;
 
      // 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
  }
}

Sub ListEntities()
    ' This example returns the first entity in model space
    On Error Resume Next
    Dim entity As AcadEntity
    If ThisDrawing.ModelSpace.count <> 0 Then
        Set entity = ThisDrawing.ModelSpace.Item(0)
        MsgBox entity.ObjectName + _
               " is the first entity in model space."
    Else
        MsgBox "There are no objects in model space."
    End If
End Sub