每個 AutoCAD 資料庫元素物件(DBObject)都可以使用擴充套件字典來儲存自定義資料。
通常這一機制用來為圖元物件（比如：線、圓等）儲存非圖形資料。
以下示例程式碼實現：
AddXRecordToEntity: 讓使用者選擇一圖元，然後在圖元的擴充套件字典中儲存自定義資料。
GetXRecordFromEntity: 讓使用者選擇一圖元，讀取圖元的擴充套件字典中儲存的自定義資料。

[CommandMethod("AddXRecordToEntity")]
public void AddXRecordToEntity()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;

    PromptEntityResult per = doc.Editor.GetEntity("\nSelect an entity: "
 
);
    if (per.Status != PromptStatus.OK)
    {
        return;
    }

    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        Entity entity = tr.GetObject(per.ObjectId, OpenMode.ForWrite) as Entity;
        if (entity.ExtensionDictionary == ObjectId.Null)
        {
            entity.CreateExtensionDictionary();
        }

        DBDictionary xDict = tr.GetObject(entity.ExtensionDictionary, OpenMode.ForRead) as
 
 DBDictionary;
        if (!xDict.Contains("CAXDEV"))
        {
            xDict.UpgradeOpen();

            Xrecord xRec = new Xrecord();
            ResultBuffer rb = new ResultBuffer();
            rb.Add(new TypedValue((int)DxfCode.Text, "Hello www.caxdev.com"));
            rb.Add(new TypedValue((int
 
)DxfCode.Int32, 123));
            rb.Add(new TypedValue((int)DxfCode.Real, 1.2345));
            xRec.Data = rb;
            xDict.SetAt("CAXDEV", xRec);

            tr.AddNewlyCreatedDBObject(xRec, true);
        }

        tr.Commit();
    }
}

[CommandMethod("GetXRecordFromEntity")]
public void GetXRecordFromEntity()
{
    Document doc = Application.DocumentManager.MdiActiveDocument;
    Database db = doc.Database;

    PromptEntityResult per = doc.Editor.GetEntity("\nSelect an entity: ");
    if (per.Status != PromptStatus.OK)
    {
        return;
    }

    using (Transaction tr = db.TransactionManager.StartTransaction())
    {
        Entity entity = tr.GetObject(per.ObjectId, OpenMode.ForRead) as Entity;
        if (entity.ExtensionDictionary != ObjectId.Null)
        {
            DBDictionary xDict = tr.GetObject(entity.ExtensionDictionary, OpenMode.ForRead) as DBDictionary;
            if (xDict.Contains("CAXDEV"))
            {
                ObjectId xRecId = xDict.GetAt("CAXDEV");
                Xrecord xRec = tr.GetObject(xRecId, OpenMode.ForRead) as Xrecord;
                if (xRec == null)
                    return;

                foreach (TypedValue tv in xRec.Data)
                {
                    doc.Editor.WriteMessage("\nTypeCode: {0}; Value: {1}", tv.TypeCode, tv.Value);
                }
            }
        }
    }
}

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