Performing an update operation is an extremely simple operation. You need a reference to an existing object in the database. Once you have it, just update its properties and invoke the well-known SaveChanges method.
Customer customerToUpdate = dbContext.Customers.First(); customerToUpdate.Fax = "[newFax]"; dbContext.SaveChanges();
Dim customerToUpdate As Customer = dbContext.Customers.First() customerToUpdate.Fax = "[newFax]" dbContext.SaveChanges()