```c#
Model Model = new Model();
System.Type[] Types = new System.Type[1];
Types.SetValue(typeof(TSM.Part), 0);

ModelObjectEnumerator parts = Model.GetModelObjectSelector().GetAllObjectsWithType(Types);

foreach (TSM.Part part in parts)
{
    // you can cast the part to an object that you are after e.g. Beam, perhaps depending on some certain properties (e.g. a certain length etc) and add that to a collection accordingly if you wish.
  Tekla.Structures.Model.Operations.Operation.DisplayPrompt("Assembly number " + part.AssemblyNumber + " " + part );
}
```