Obtaining the Class type from an ObjectId (not having to open for read)

by Fenton Webb

I’m sure you have all seen code like this before, where you open an entity in the DWG database to find out its type…

Database db =

Application.DocumentManager.MdiActiveDocument.Database;

using (Transaction trans = db.TransactionManager.StartTransaction())

{

  // open the entities

  Entity ent1 = (Entity)trans.GetObject(id1, OpenMode.ForRead);

  Entity ent2 = (Entity)trans.GetObject(id2, OpenMode.ForRead);

  // find their type

 

Type entType1 = ent1.GetType();

  Type entType2 = ent2.GetType();

  // the two entities should be the same type

  if (!entType1.Equals(entType2))

    return;

  // …

There’s a much more efficient way to obtain the class name/entity type… That’s using ObjectId.ObjectClass property.

Using this property saves you opening an object for read, thus saving valuable CPU cycles.

e.g.

// the two entities should be the same type

if (id1.ObjectClass.Name != id2.ObjectClass.Name))

  return;

Database db =

Application.DocumentManager.MdiActiveDocument.Database;

using (Transaction trans = db.TransactionManager.StartTransaction())

{

// open the entities

Entity ent1 = (Entity)trans.GetObject(id1, OpenMode.ForRead);

Entity ent2 = (Entity)trans.GetObject(id2, OpenMode.ForRead);

// …