Copy a row from datarow to another able

Http://www.cnblogs.com/pains/archive/2007/11/22/969003.html

The following two methods are used to copy a row from datarow to another able. An error "this row already belongs to another table" will occur during direct Add. In fact, we know how to do this before, but I am confused every time I use it. I will write them down this time.
1. Use datarow.Itemarray
Datatable T = new datatable ();
Datarow r = T. newrow ();
R.Itemarray= Oldrow. Itemarray;
T. Rows. Add (R );

2. Use datatable.Importrow()
T.Importrow(Oldrow );