Declaratively configure WCF behavior extension on programmatically constructed endpoint

I have a WCF behavior extension that I would like to add to a WCF client. However, the client is constructed programmatically. The endpoint address may vary, but I know the type. I could add the behavior programmatically or in the config file (preferred), but I need to pass some configuration in the config file only.

I don't want this in Common behaviors (machine.config).

I can add the behavior programmatically

endpoint.Behaviors.Add(new MyCustomBehavior())

But I'd rather do it in config, so I can configure the extension there as well.

Is it possible to declaratively add and configure an endpoint behavior extension to a programmatically constructed endpoint knowing only the the type or interface while leaving the client endpoint to be constructed programmatically?

<system.serviceModel>
  <client>
    <!-- Created programmatically -->
  </client>
<extensions>
  <behaviorExtensions>
    <add name="MyCustomBehavior" type="namespace.CustomBehaviors", MyAssembly, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null" />
  </behaviorExtensions>   
</extensions>
  <behaviors>
    <endpointBehaviors>
      <behavior name="MyCustomBehavior">
        <MyCustomBehavior MyImportantBehaviorParam1="foo"  />
      </behavior>
    </endpointBehaviors>   
  </behaviors>
</system.serviceModel>

Of course I could put the config in another section, and have my behavior read it there, but I'd rather use the WCF facilities if possible.

To do that you need to create a behavior configuration extension for your endpoint. For more information on how to do that, check https://learn.microsoft.com/en-us/archive/blogs/carlosfigueira/wcf-extensibility-behavior-configuration-extensions.

Update: I see your issue now. There's no direct way to add to an endpoint created via code a behavior declared in configuration. You can still do it, though, but you'll need to use some reflection to access the CreateBehavior method of the behavior configuration extension (the method is protected) to actually create the endpoint behavior to add it to the endpoint created via code. The code below shows how this can be done.

public class StackOverflow_10232385
{
    public class MyCustomBehavior : IEndpointBehavior
    {
        public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
        {
            Console.WriteLine("In {0}.{1}", this.GetType().Name, MethodBase.GetCurrentMethod().Name);
        }

        public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
        {
            Console.WriteLine("In {0}.{1}", this.GetType().Name, MethodBase.GetCurrentMethod().Name);
        }

        public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
        {
            Console.WriteLine("In {0}.{1}", this.GetType().Name, MethodBase.GetCurrentMethod().Name);
        }

        public void Validate(ServiceEndpoint endpoint)
        {
            Console.WriteLine("In {0}.{1}", this.GetType().Name, MethodBase.GetCurrentMethod().Name);
        }
    }

    public class MyCustomBehaviorExtension : BehaviorExtensionElement
    {
        public override Type BehaviorType
        {
            get { return typeof(MyCustomBehavior); }
        }

        protected override object CreateBehavior()
        {
            return new MyCustomBehavior();
        }
    }

    [ServiceContract]
    public interface ITest
    {
        [OperationContract]
        string Echo(string text);
    }
    public class Service : ITest
    {
        public string Echo(string text)
        {
            return text;
        }
    }

    public static void Test()
    {
        string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
        ServiceHost host = new ServiceHost(typeof(Service), new Uri(baseAddress));
        ServiceEndpoint endpoint = host.AddServiceEndpoint(typeof(ITest), new BasicHttpBinding(), "");

        var configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
        ServiceModelSectionGroup smsg = configuration.GetSectionGroup("system.serviceModel") as ServiceModelSectionGroup;
        EndpointBehaviorElement endpointBehaviorElement = smsg.Behaviors.EndpointBehaviors["MyCustomBehavior_10232385"];
        foreach (BehaviorExtensionElement behaviorElement in endpointBehaviorElement)
        {
            MethodInfo createBehaviorMethod = behaviorElement.GetType().GetMethod("CreateBehavior", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public, null, Type.EmptyTypes, null);
            IEndpointBehavior behavior = createBehaviorMethod.Invoke(behaviorElement, new object[0]) as IEndpointBehavior;
            endpoint.Behaviors.Add(behavior);
        }

        host.Open();
        Console.WriteLine("Host opened");

        ChannelFactory<ITest> factory = new ChannelFactory<ITest>(new BasicHttpBinding(), new EndpointAddress(baseAddress));
        ITest proxy = factory.CreateChannel();
        Console.WriteLine(proxy.Echo("Hello"));

        ((IClientChannel)proxy).Close();
        factory.Close();

        Console.Write("Press ENTER to close the host");
        Console.ReadLine();
        host.Close();
    }
}

And the configuration for this code:

<system.serviceModel>
    <extensions>
        <behaviorExtensions>
            <add name="myCustomBehavior_10232385" type="QuickCode1.StackOverflow_10232385+MyCustomBehaviorExtension, QuickCode1"/>
        </behaviorExtensions>
    </extensions>
    <behaviors>
        <endpointBehaviors>
            <behavior name="MyCustomBehavior_10232385">
                <myCustomBehavior_10232385/>
            </behavior>
        </endpointBehaviors>
    </behaviors>
</system.serviceModel>