Serialize a .NET class into an AutoCAD drawing database

By Adam Nagy

I would like to serialize my .NET class into an AutoCAD drawing database, so it is saved into the drawing, and I can recreate my class again (deserialize it), when the drawing is reopened. How could I do it?

Solution

You could use the .NET serialization technique to serialize your class into a binary stream and then you can save it in the drawing as a bunch of binary chunks. You could save the ResultBuffer to an object’s XData or into an Xrecord.Data of an entity or an item in the Named Objects Dictionary (NOD). DevNote TS2563 tells you what the difference is between using XData and Xrecord. If you are saving it into an XData, then the ResultBuffer needs to start with a registered application name. Here is a sample which shows this:

using System; using System.Runtime.Serialization; using System.Runtime.Serialization.Formatters.Binary; using System.IO; using System.Security.Permissions;   using Autodesk.AutoCAD.Runtime; using acApp = Autodesk.AutoCAD.ApplicationServices.Application; using Autodesk.AutoCAD.DatabaseServices; using Autodesk.AutoCAD.EditorInput;   [assembly: CommandClass(typeof(MyClassSerializer.Commands))]   namespace MyClassSerializer {   // We need it to help with deserialization     public sealed class MyBinder : SerializationBinder   {     public override System.Type BindToType(       string assemblyName,       string typeName)     {       return Type.GetType(string.Format("{0}, {1}",         typeName, assemblyName));     }   }     // Helper class to write to and from ResultBuffer     public class MyUtil   {     const int kMaxChunkSize = 127;       public static ResultBuffer StreamToResBuf(       MemoryStream ms, string appName)     {       ResultBuffer resBuf =          new ResultBuffer(           new TypedValue(             (int)DxfCode.ExtendedDataRegAppName, appName));         for (int i = 0; i < ms.Length; i += kMaxChunkSize)       {         int length = (int)Math.Min(ms.Length - i, kMaxChunkSize);         byte[] datachunk = new byte[length];         ms.Read(datachunk, 0, length);         resBuf.Add(           new TypedValue(             (int)DxfCode.ExtendedDataBinaryChunk, datachunk));       }         return resBuf;     }       public static MemoryStream ResBufToStream(ResultBuffer resBuf)     {       MemoryStream ms = new MemoryStream();       TypedValue[] values = resBuf.AsArray();         // Start from 1 to skip application name         for (int i = 1; i < values.Length; i++)       {         byte[] datachunk = (byte[])values[i].Value;         ms.Write(datachunk, 0, datachunk.Length);       }       ms.Position = 0;         return ms;     }   }     [Serializable]   public abstract class MyBaseClass : ISerializable   {     public const string appName = "MyApp";       public MyBaseClass()     {     }       public static object NewFromResBuf(ResultBuffer resBuf)     {       BinaryFormatter bf = new BinaryFormatter();       bf.Binder = new MyBinder();         MemoryStream ms = MyUtil.ResBufToStream(resBuf);         MyBaseClass mbc = (MyBaseClass)bf.Deserialize(ms);         return mbc;     }       public static object NewFromEntity(Entity ent)     {       using (         ResultBuffer resBuf = ent.GetXDataForApplication(appName))       {         return NewFromResBuf(resBuf);       }     }       public ResultBuffer SaveToResBuf()     {       BinaryFormatter bf = new BinaryFormatter();       MemoryStream ms = new MemoryStream();       bf.Serialize(ms, this);       ms.Position = 0;         ResultBuffer resBuf = MyUtil.StreamToResBuf(ms, appName);         return resBuf;     }       public void SaveToEntity(Entity ent)     {       // Make sure application name is registered       // If we were to save the ResultBuffer to an Xrecord.Data,       // then we would not need to have a registered application name         Transaction tr =          ent.Database.TransactionManager.TopTransaction;         RegAppTable regTable =         (RegAppTable)tr.GetObject(           ent.Database.RegApp
TableId, OpenMode.ForWrite);       if (!regTable.Has(MyClass.appName))       {         RegAppTableRecord app = new RegAppTableRecord();         app.Name = MyClass.appName;         regTable.Add(app);         tr.AddNewlyCreatedDBObject(app, true);       }         using (ResultBuffer resBuf = SaveToResBuf())       {         ent.XData = resBuf;       }     }       [SecurityPermission(SecurityAction.LinkDemand,        Flags = SecurityPermissionFlag.SerializationFormatter)]     public abstract void GetObjectData(       SerializationInfo info, StreamingContext context);   }     [Serializable]   public class MyClass : MyBaseClass   {     public string myString;     public double myDouble;       public MyClass()     {     }       protected MyClass(       SerializationInfo info, StreamingContext context)     {       if (info == null)         throw new System.ArgumentNullException("info");         myString = (string)info.GetValue("MyString", typeof(string));       myDouble = (double)info.GetValue("MyDouble", typeof(double));     }       [SecurityPermission(SecurityAction.LinkDemand,        Flags = SecurityPermissionFlag.SerializationFormatter)]     public override void GetObjectData(       SerializationInfo info, StreamingContext context)     {       info.AddValue("MyString", myString);       info.AddValue("MyDouble", myDouble);     }       // Just for testing purposes       public override string ToString()     {       return base.ToString() + "," +          myString + "," + myDouble.ToString();     }   }     public class Commands   {     [CommandMethod("SaveClassToEntityXData")]     static public void SaveClassToEntityXData()     {       Database db = acApp.DocumentManager.MdiActiveDocument.Database;       Editor ed = acApp.DocumentManager.MdiActiveDocument.Editor;         PromptEntityResult per =          ed.GetEntity("Select entity to save class to:n");       if (per.Status != PromptStatus.OK)         return;         // Create an object         MyClass mc = new MyClass();       mc.myDouble = 1.2345;       mc.myString = "Some text";         // Save it to the document         using (         Transaction tr = db.TransactionManager.StartTransaction())       {         Entity ent =            (Entity)tr.GetObject(per.ObjectId, OpenMode.ForWrite);           mc.SaveToEntity(ent);           tr.Commit();       }         // Write some info about the results         ed.WriteMessage(         "Content of MyClass we serialized:n {0} n", mc.ToString());     }       [CommandMethod("GetClassFromEntityXData")]     static public void GetClassFromEntityXData()     {       Database db = acApp.DocumentManager.MdiActiveDocument.Database;       Editor ed = acApp.DocumentManager.MdiActiveDocument.Editor;         PromptEntityResult per =          ed.GetEntity("Select entity to get class from:n");       if (per.Status != PromptStatus.OK)         return;         // Get back the class          using (         Transaction tr = db.TransactionManager.StartTransaction())       {         Entity ent =            (Entity)tr.GetObject(per.ObjectId, OpenMode.ForRead);           MyClass mc = (MyClass)MyClass.NewFromEntity(ent);           // Write some info about the results           ed.WriteMessage(           "Content of MyClass we deserialized:n {0} n",            mc.ToString());           tr.Commit();       }     }   } }