Custom WCF Behaviors Through App.Config

You can create extension elements in your WCF configuration files in order to support introducing custom behaviors (such as IEndpointBehavior-implementations) into the processing pipeline in a declarative manner. However, the documentation online at this moment isn't too clear on the issue (well, it's outdated, so of course it's not clear!).

Doing it fortunately is not hard; here's how to:

1. Create your custom behavior configuration element by creating a class that derives from the System.ServiceModel.Configuration.BehaviorExtensionElement class.

2. Add any properties you need to the class to represent attributes in the configuration element, and mark them with the [ConfigurationElement] attribute. For example:

///

[ConfigurationProperty("notice", DefaultValue="", IsRequired=true)]

public string Notice

{

   get { return (string)base["notice"]; }

   set { base["notice"] = value; }

}

3. Override the BehaviorType property and return the type of the behavior your configuration element will introduce into the pipeline:

/// 


/// Return the type of the behavior we configure
/// 

public override Type BehaviorType
{
   get { return typeof(WsdlNoticeBehavior); }
}

4. Override the CreateBehavior() method; this is where you create and return an instance of your custom behavior based on the properties you hold from the configuration element:

/// 


/// Create an instance of the behavior
/// we represent
/// 

/// The WsdlNoticeBehavior instance
protected override object CreateBehavior()
{
   return new WsdlNoticeBehavior(Notice);
}

5. You'll likely want to override the Properties property and the CopyFrom() method as well:

private ConfigurationPropertyCollection _properties; 

/// 


/// Return a collection of all our properties
/// 

protected override ConfigurationPropertyCollection Properties
{
   get
   {
      if ( _properties == null )
      {
         _properties = new ConfigurationPropertyCollection();
         _properties.Add(new ConfigurationProperty(
            "notice", typeof(string), "",
            ConfigurationPropertyOptions.IsRequired
            ));
      }
      return _properties;
   }
}

/// 


/// Copy the information of another element into
/// ourselves
/// 
/// 
The element from which to copy
public override void CopyFrom(ServiceModelExtensionElement from)
{
   base.CopyFrom(from);
   WsdlNoticeElement element = (WsdlNoticeElement)from;
   Notice = element.Notice;
}

After this, you're ready to introduce your behavior into the configuration file. First, you need to register your custom behavior configuration element by adding it in the // element:

<extensions>
   <behaviorExtensions>
      <add name="wsdlNotice" 
           type="Winterdom.ServiceModel.Extensions.Configuration.WsdlNoticeElement, 
Winterdom.ServiceModel.Extensions, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"
           />
   behaviorExtensions>
extensions>

Now you can use your custom element in the correct behaviors collection:

<behaviors>
   <endpointBehaviors>
      <behavior name="EndpointBehaviors">
         <wsdlNotice notice="This is a notice"/>
      behavior>
   endpointBehaviors>
behaviors>

That's it!