This example updates an Empoyee without first loading it.

Employees emp = new Employees(); 
emp.AddNew();             // Merely creates the DataTable = RowState = Added 
emp.EmployeeID = 1; 
emp.AcceptChanges();      // Mark the record as DataRowState.Unchanged 
emp.FirstName = "Direct"; // Any column change marks the record as DataRowState.Modified 
emp.LastName = "Updates"; 
emp.Save(); 

The perferred way is still:

Employee emp = new Employee(); 
emp.LoadByPrimaryKey(1); 
emp.FirstName = "Direct"; 
emp.LastName = "Updates"; 
emp.Save(); 

This is the perferred way for for several reasons. First, down the road you encounter bottlenecks, but discover that the solution is to switch from your default of DynamicSQL to StoredProcedure. If you used the preferred approach you have a 1 line change to your config file and you are good to go. The non-preferred method doesn't allow for the use of stored procedures and relies entirely on dynamic sql. Also, and more importanly, you have no concurrency handling possibiliites in the non-preferred sample.