WCF Essentials (7)

10. 使用通道

我们可以用通道(channel)代替静态代理(svcutil proxy)，直接调用服务操作。ChannelFactory<T> 允许我们在运行时动态创建一个代理与服务进行交互。

public class ContractDescription
{
  public Type ContractType {get;set;}
  //More members
}

public class ServiceEndpoint
{
  public ServiceEndpoint(ContractDescription contract, Binding binding, EndpointAddress address);
  public EndpointAddress Address {get;set;}
  public Binding Binding {get;set;}
  public ContractDescription Contract {get;}
  //More members
}

public abstract class ChannelFactory : ...
{
  public ServiceEndpoint Endpoint {get;}
  //More members
}

public class ChannelFactory<T> : ChannelFactory,...
{
  public ChannelFactory(ServiceEndpoint endpoint);
  public ChannelFactory(string configurationName);
  public ChannelFactory(Binding binding, EndpointAddress endpointAddress);
  public static T CreateChannel(Binding binding, EndpointAddress endpointAddress);
  public T CreateChannel( );
  //More Members
}

我 们需要从配置文件中获取一个端点配置名称，将其提交给 ChannelFactory<T> 构造方法，也可以直接使用相应的绑定和地址对象作为参数。然后，调用 CreateChannel() 方法获取动态生成代理对象的引用。有两种方法关闭代理，将通道转型成 IDisposable，并调用 Dispose() 方法关闭代理；或者转型成 ICommunicationObject，调用 Close() 方法。

ChannelFactory<IMyContract> factory = new ChannelFactory<IMyContract>( );

IMyContract proxy1 = factory.CreateChannel( );
using(proxy1 as IDisposable)
{
  proxy1.MyMethod( );
}

IMyContract proxy2 = factory.CreateChannel( );
proxy2.MyMethod( );
ICommunicationObject channel = proxy2 as ICommunicationObject;
Debug.Assert(channel != null);
channel.Close( );

注: 通道对象除了实现服务契约接口外，还实现了 System.ServiceModel.IClientChannel。

public interface IClientChannel : IContextChannel, IChannel, ICommunicationObject, IDisposable ...
{
}

除创建 ChannelFactory<T> 对象实例外，我们还可以直接使用静态方法 CreateChannel() 来创建代理。不过这需要我们提供端点地址和绑定对象。

Binding binding = new NetTcpBinding( );
EndpointAddress address = new EndpointAddress("net.tcp://localhost:8000");

IMyContract proxy = ChannelFactory<IMyContract>.CreateChannel(binding, address);
using(proxy as IDisposable)
{
  proxy1.MyMethod( );
}