继承泛型类T必须是引用类型

Question

public class _Base_Client<T> : System.ServiceModel.ClientBase<T>

It complains that The type 'T' must be a reference type in order to use it as parameter 'TChannel'

T is a reference to an interface.

Here is the line I wish to change to use the new base class

public class EchoServiceClient : 
    System.ServiceModel.ClientBase<IEchoService>, IEchoService

How can I fix this? thanks

Answer 1

Change:

public class _Base_Client<T> : System.ServiceModel.ClientBase<T>

To:

public class _Base_Client<T> : System.ServiceModel.ClientBase<T> where T : class

The constraints in your class must be at least as strict as the constraints defined in its base class ( ClientBase ). To wit, here is the declaration of ClientBase :

public abstract class ClientBase<TChannel> : ICommunicationObject, 
    IDisposable where TChannel : class

Notice the class constraint.

Answer 2

You can't use the interface in there. You need a concrete implementation of IEchoService .