卸载外部参照 （.NET）

若要卸载外部参照，请使用以下方法。卸载当前图形中未使用的参照文件时，由于不必读取和显示不必要的图形几何图形或符号表信息，因此 AutoCAD 性能得到增强。在重新加载外部参照之前，外部参照几何和任何嵌套外部参照的几何图形不会显示在当前图形中。Unload

Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Geometry

<CommandMethod("UnloadingExternalReference")> _
Public Sub UnloadingExternalReference()
    ' Get the current database and start a transaction
    Dim acCurDb As Autodesk.AutoCAD.DatabaseServices.Database
    acCurDb = Application.DocumentManager.MdiActiveDocument.Database

    Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
        ' Create a reference to a DWG file
        Dim PathName As String = "C:\AutoCAD\Sample\Sheet Sets\Architectural\Res\Exterior Elevations.dwg"
        Dim acXrefId As ObjectId = acCurDb.AttachXref(PathName, "Exterior Elevations")

        ' If a valid reference is created then continue
        If Not acXrefId.IsNull Then
            ' Attach the DWG reference to the current space
            Dim insPt As New Point3d(1, 1, 0)
            Using acBlkRef As New BlockReference(insPt, acXrefId)

                Dim acBlkTblRec As BlockTableRecord
                acBlkTblRec = acTrans.GetObject(acCurDb.CurrentSpaceId, OpenMode.ForWrite)

                acBlkTblRec.AppendEntity(acBlkRef)
                acTrans.AddNewlyCreatedDBObject(acBlkRef, True)
            End Using

            MsgBox("The external reference is attached.")

            Using acXrefIdCol As New ObjectIdCollection
                acXrefIdCol.Add(acXrefId)

                acCurDb.UnloadXrefs(acXrefIdCol)
            End Using

            MsgBox("The external reference is unloaded.")
        End If

        ' Save the new objects to the database
        acTrans.Commit()

        ' Dispose of the transaction
    End Using
End Sub

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;

[CommandMethod("UnloadingExternalReference")]
public void UnloadingExternalReference()
{
    // Get the current database and start a transaction
    Database acCurDb;
    acCurDb = Application.DocumentManager.MdiActiveDocument.Database;

    using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
    {
        // Create a reference to a DWG file
        string PathName = "C:\\AutoCAD\\Sample\\Sheet Sets\\Architectural\\Res\\Exterior Elevations.dwg";
        ObjectId acXrefId = acCurDb.AttachXref(PathName, "Exterior Elevations");

        // If a valid reference is created then continue
        if (!acXrefId.IsNull)
        {
            // Attach the DWG reference to the current space
            Point3d insPt = new Point3d(1, 1, 0);
            using (BlockReference acBlkRef = new BlockReference(insPt, acXrefId))
            {
                BlockTableRecord acBlkTblRec;
                acBlkTblRec = acTrans.GetObject(acCurDb.CurrentSpaceId, OpenMode.ForWrite) as BlockTableRecord;

                acBlkTblRec.AppendEntity(acBlkRef);
                acTrans.AddNewlyCreatedDBObject(acBlkRef, true);
            }

            Application.ShowAlertDialog("The external reference is attached.");

            using (ObjectIdCollection acXrefIdCol = new ObjectIdCollection())
            {
                acXrefIdCol.Add(acXrefId);

                acCurDb.UnloadXrefs(acXrefIdCol);
            }

            Application.ShowAlertDialog("The external reference is unloaded.");
        }

        // Save the new objects to the database
        acTrans.Commit();

        // Dispose of the transaction
    }
}

Sub UnloadingExternalReference()
    ' Define external reference to be inserted
    Dim xrefInserted As AcadExternalReference
    Dim insertionPnt(0 To 2) As Double
    Dim PathName As String
    insertionPnt(0) = 1
    insertionPnt(1) = 1
    insertionPnt(2) = 0
    PathName = "C:\AutoCAD\Sample\Sheet Sets\Architectural\Res\Exterior Elevations.dwg"
 
    ' Add the external reference
    Set xrefInserted = ThisDrawing.ActiveLayout.Block. _
        AttachExternalReference(PathName, "Exterior Elevations", insertionPnt, 1, 1, 1, 0, False)
    MsgBox "The external reference is attached."
 
    ' Unload the external reference definition
    ThisDrawing.Blocks.Item(xrefInserted.name).Unload
    MsgBox "The external reference is unloaded."
End Sub