WCF C# - Getting Specific Configuration Values From App.config

Question

I have a WCF service XYZ that will be deployed on a number of hosts. Each such service may have a connection to another XYZ service deployed on one of the other hosts. It's a distributed system where the states will differ between the services.

In order to communicate it doesn't really make sense for me to "Add Service Reference" in Visual Studio because that will just add redundancy (the service already knows what it's going to be communicating with).

So currently my idea is to specify the other service endpoints in the App.config files of each service. For example:

<client>
  <endpoint name="BEL" 
            address="tcp://us.test.com:7650/OrderManagementService"
            binding="tcpBinding"
            contract="IOrderManagementService"/>
  <endpoint name="BEL2"
      address="tcp://us.test2.com:7650/OrderManagementService"
      binding="tcpBinding"
      contract="IOrderManagementService"/>
</client>

Now, I just want a way to read these settings and create ChannelFactories and Channels in my code. However, it's turning out to be a hassle to do this.

Two questions: am I doing things right; and if so, what's the best way to extract these values from the config file?

this question stackoverflow.com/questions/297431/… might help — Niall Gray
– Niall Gray, Commented Jul 20, 2011 at 18:50

Christian Hayter · Accepted Answer · 2011-07-20 19:01:27Z

3

Creating channels directly isn't hard, and all the endpoint configuration is read in for you. Try something like this:

var factory = new ChannelFactory<IOrderManagementService>("BEL");
var proxy = factory.CreateChannel();
// call methods on proxy
proxy.Close();

Note that the proxy needs closing properly (which means calling Close or Abort correctly) as soon as you have finished with it. However, you can leave the factory open for long periods, even in a cache.

You can encapsulate this into helper methods to make the calling code simple:

public static ChannelFactory<TContract> NewChannelFactory<TContract>(string endpointConfigurationName) where TContract : class {
    // TODO: Cache the factory in here for better performance.
    return new ChannelFactory<TContract>(endpointConfigurationName);
}

public static void Invoke<TContract>(ChannelFactory<TContract> factory, Action<TContract> action) where TContract : class {
    var proxy = (IClientChannel) factory.CreateChannel();
    bool success = false;
    try {
        action((TContract) proxy);
        proxy.Close();
        success = true;
    } finally {
        if(!success) {
            proxy.Abort();
        }
    }
}

edited Jul 20, 2011 at 19:01

answered Jul 20, 2011 at 18:50

Christian Hayter

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5 Comments

UmaN Over a year ago

Thanks, I didn't know that the endpoint configuration was automatically read in for me!

Richard Blewett Over a year ago

strange formulation - why not just catch an exception, abort the channel and rethrow?

Christian Hayter Over a year ago

@Richard: Catching and re-throwing an exception takes time and removes part of the stack trace. If those things are not relevant to your code, that's fine, but it costs nothing to avoid the situation.

Richard Blewett Over a year ago

Granted that it is slower but this is a rarely executed code path you would hope and the intent of the code is very clear. You lose no information if you use the general throw clause

Christian Hayter Over a year ago

Close can just as easily throw an exception as the rest of the code. If that happens, you still want Abort to be called. If you don't use the above pattern you need two nested catch blocks, which seems uglier to me.

Patrick Desjardins · Accepted Answer · 2011-07-20 18:48:44Z

0

WebConfigurationManager can be used to get your Endpoints. You have a client section so in the GetSection just pass it through like the code above.

ClientSection clientSection = (WebConfigurationManager.GetSection("system.serviceModel/client") as ClientSection);

foreach(ChannelEndpointElement cee in clientSection.Endpoints)
{
    // Store your endpoint for future use with ChannelFactories 
}

answered Jul 20, 2011 at 18:48

Patrick Desjardins

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Comments

Tod · Accepted Answer · 2011-07-20 18:57:54Z

If I understand your question correctly it's similar to something I wanted to do. I didn't want to include Service References in every library or app that needed access to the service. I created a Mediator pattern class that did have a service reference and served as a proxy to the service. It took an endpoint string as the only class constructor argument. The constructor looked like this (I threw in a channel factory example as a comment)

    public DspServiceMediator( String serviceAddress)
    {
        EndpointAddress end_point = new EndpointAddress(serviceAddress);
        NetTcpBinding new_tcp = new NetTcpBinding(SecurityMode.None);
        new_tcp.ReceiveTimeout = TimeSpan.MaxValue;
        new_tcp.SendTimeout = new TimeSpan(0, 0, 30); //30 seconds
        //_channelFactory = new ChannelFactory<DspServiceClient>(new_tcp, end_point);
        _dspClient = new DspServiceClient(new_tcp, end_point);
    }

I actually replicated each property in the service (many times I had little mods that made the service easier to use by the final client) but you could just violate the law of Demeter in your client code and return the underlying service client (_dspClient in the code above) and use that.

landoncz · Accepted Answer · 2011-07-20 19:12:22Z

Since all your connections are the same contract, and essentially the same client code, you can use the same ChannelFactory to create as many ServiceChannels as you need, and you can connect each ServiceChannel to different EndpointAddresses as specified in regular old application settings, or in a database:

private List<string> _endpointLists = new List<string>() { "127.0.0.0:1234" };
private static ChannelFactory<IWCFServiceChannel> _channelFactory = new ChannelFactory<ServiceReference.IWCFServiceChannel>("App.config Binding Name Here");
private List<WCFServiceChannel> _serviceChannels = new List<WCFServiceChannel>();

foreach (string uriEndpoint in _endpointLists)
    _serviceChannels.Add(_channelFactory.CreateChannel(new EndpointAddress(uriEndpoint)));

_serviceChannels[0].Open();
...

And you can do this as many times as you need to, using the same ChannelFactory, but creating new ServiceChannels with different endpoints each time.

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