What's the best way to respond with the correct content type from request filter in ServiceStack?

Question

ServiceStack services are great for responding with the content type that's requested in the Accept header. But if I need to close/end the response early from within a request filter, is there a way to respond with the proper content type? All I have access to in a request filter is the raw IHttpResponse so it seems to me that the only option is to tediously, manually check the Accept header and do a bunch of switch/case statements to figure out which serializer to use and then write directly to the response.OutputStream.

To further illustrate the question, in a normal service method you can do something like this:

public object Get(FooRequest request)
{
    return new FooResponseObject()
    {
        Prop1 = "oh hai!"
    }
}

And ServiceStack will figure out what content type to use and which serializer to use. Is there anything similar to this that I can do within a request filter?

Answer 1

ServiceStack pre-calculates the Requested Content-Type on a number of factors (e.g. Accept: header, QueryString, etc) it stores this info in the httpReq.ResponseContentType property.

You can use this along with the IAppHost.ContentTypeFilters registry which stores a collection of all Registered Content-Type serializers in ServiceStack (i.e. built-in + Custom) and do something like:

var dto = ...;
var contentType = httpReq.ResponseContentType;
var serializer = EndpointHost.AppHost
    .ContentTypeFilters.GetResponseSerializer(contentType);

if (serializer == null)
   throw new Exception("Content-Type {0} does not exist".Fmt(contentType));

var serializationContext = new HttpRequestContext(httpReq, httpRes, dto);
serializer(serializationContext, dto, httpRes);
httpRes.EndServiceStackRequest(); //stops further execution of this request

Note: this just serializes the Response to the Output stream, it does not execute any other Request or Response filters or other user-defined hooks as per a normal ServiceStack request.