var client = Client.GetClient(2)
client.FirstName = "Иванов"

public Model.Client UpdateClient (Model.Client client)
		{
			using (var db = Model.MyDataContext.CreateContext())
			{
				db.Client.Attach(client);
				db.Refresh(System.Data.Linq.RefreshMode.KeepChanges, client);
				db.SubmitChanges();
			}
			return client;
		}