using (TransactionScope scope = new TransactionScope())
using (var context = new dwfEntities())
{
var field = (from x in context.DynFields where x.Id == id select
in case SQL CE does not support transaction scope, you can surely use the normal transactional approach, connection.BeginTransaction then transaction.Commit or Rollback...
If the connection is opened outside of the transaction scope you need to explicitly call EnlistTransaction. You cannot implicitly use a connection with a transaction scope in SQL CE as described here