Question

I want to create a global option that when a REST call contains &format=json to output the response as a JSON string.

If I enter the following String in my method it works:

WebOperationContext.Current.OutgoingResponse.Format = WebMessageFormat.Json;

However, if I add this line, anywhere in my Global.asax file, I get a nullException for Current Context:

String format = "";

if (HttpContext.Current.Request.QueryString["format"] != null)
  format = HttpContext.Current.Request.QueryString["format"];

if (String.Equals("json", format, StringComparison.OrdinalIgnoreCase))
  System.ServiceModel.Web.WebOperationContext.Current.OutgoingResponse.Format = System.ServiceModel.Web.WebMessageFormat.Json;

The exception is triggered here:

System.ServiceModel.Web.WebOperationContext.Current

Anyone know how I can add this functionality globally (WCF)?

Answer 1

You can add your own DispatchMessageInspector to WCF processing pipeline via service behavior. Here is how to do that.

To apply behavior via config file at first you should derive new class from BehaviorExtensionElement and override members BehaviorType and CreateBehavior.
Then add to config section similar to that (with your full type name)

<system.serviceModel>
    <extensions>
        <behaviorExtensions>
            <add name="myBehavior" type="SomeNamespace.MyBehaviorExtensionElement, AssemblyName,
                Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
       </behaviorExtensions>
    </extensions>
</system.serviceModel>

and that

<behaviors>
    <behavior configurationName="myServiceBehavior">
        <myBehavior />            
    </behavior>
</behaviors>

Finally apply this configuration to your service.