Creating and Closing of WCF Proxies

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Introduction

This tip discusses how to use DynamicProxy to hide the fact that a WCF proxy is closed after each call and re-created.

Background

Creating a WPF application using MVVM we had code, like view models calling services, or actually being dependent on an interface which would then be a service proxy. I wanted to have the proxy closed after each call (which is another discussion), but I didn't want the user of the proxy to have any knowledge of ICommunicationObject, because it would make testing harder and make things more complex. In general, I wanted to mock the service interface in my unit tests.

So I wanted to hide the fact that the implementation was in fact a service proxy and let the implementation handle the configuration, creation and closing of the channel.

Using the Code

The first thing I made was a small helper class, ProxyWrapper, that would ensure proper closing of the proxy. If the service is faulted, Abort() should be called, etc.

ProxyWrapper.Use(m_ChannelFactory.CreateChannel, proxy =>
{ 
   proxy.ServiceMethod();
} 

After that, I looked into dynamic proxy generation using Castle.Core DynamicProxy. This came in handy, because I could dynamically create a class that implemented the ServiceContract from where I could intercept each call to any method on the proxy. Intercept the method call, create the channel using a reusable ChannelFactory, pass through the method arguments to the real instance of the proxy, and close the proxy after use.

This is how you create your reusable proxy instance.

var address = "net.tcp://localhost:5465/Service";

var serviceFactory = new ServiceFactory<IService>();
var proxy  = serviceFactory.CreateChannel(address, new NetTcpBinding());

Other configuration method could easily be created as needed.

Points of Interest

Remember to always reuse a ProxyGenerator class. For each ProxyGenerator you get, a new assembly will be created. This could lead to a "memory leak".

The ServiceFactory also hooks nice and easily into any IoC container. With Unity, you would use an InjectionFactory.