TPH inheritance 查询的 3 种写法

TPHinheritance 查询的 3 种写法

var USACustomers1 = from c inNWEntities.BaseCustomers

                    where c is USACustomer

                    select c;

var USACustomers2 = from c inNWEntities.BaseCustomers.OfType<USACustomer>()

                    select c;

var USACustomers3 = from c inNWEntities.BaseCustomers

                    select c as USACustomer;

Console.WriteLine("Total number of USAcustomers (is): {0}", USACustomers1.Count());

Console.WriteLine("Total number of USAcustomers (ofType): {0}", USACustomers2.Count());

Console.WriteLine("Total number of USAcustomers (as): {0}", USACustomers3.Count(i => i != null));

 

第三种写法必须加上I <> null 的条件。