ServiceStack deserialization of JSON content in multipart/form-data request - rest

Question

I'm creating a RESTful service using ServiceStack that should consume a POST with multipart/form-data content. The content is in JSON format, but when I send the POST, the object is not deserialized correctly (all properties are null/default values). If I try just sending that object as a regular POST (without the multipart/form-data), it deserializes just fine.
I poked around in the ServiceStack code to try to figure out what was going on, and this is my current understanding:
HttpListenerRequestWrapper::LoadMultiPart() is loading the multipart request and saving the (non-file) parts to "FormData", which maps the name of the part to its contents. However, it appears the content-type (which is correctly written to the HttpMultiPart::Element as the individual sections are being parsed) is lost because it isn't stored in anywhere.
Some time later in control-flow, EndpointHandlerBase::DeserializeHttpRequest() calls KeyValueDataContractDeserializer.Instance.Parse() with the FormData and the type to deserialize to.
If this is the first time that kind of object is being deserialized, a StringMapTypeDeserializer is created for that type and cached to typeStringMapSerializerMap. For each property of the type, we call JsvReader.GetParseFn() to get a ParseStringDelegate to parse that deserialize that property.
The created/cached StringMapTypeDeserializer is then used to deserialize the object, using all the "ParseFn's" set earlier... which all treat the content as JSV format.
I confirmed that JsvReader.ParseFnCache has a bunch of types in it, while JsonReader.ParseFnCache is empty. Also, if I change my request to remove all quotes (i.e. turn it from JSON into JSV format), it deserializes correctly. The one weird thing is that one of the properties of my object is a Dictionary, and that deserializes correctly, even when it's in JSON format; I'm assuming this is just a fortunate coincidence (?!?).
Am I correct in my understanding of what's going on here? Is this a known limitation in ServiceStack? Bug? Is there anyway to work around it other than putting my object in a file and manually calling JsonSerializer.DeserializeFromStream()?
Thanks!
jps
Also, just incase it's useful, here's the relevant request and data-objects:
POST /api/Task HTTP/1.1
Accept: application/json
Content-Type: multipart/form-data; boundary=Boundary_1_1161035867_1375890821794
MIME-Version: 1.0
Host: localhost:12345
Content-Length: 385
--Boundary_1_1161035867_1375890821794
Content-Type: application/json
Content-Disposition: form-data; name="MyMap"
{"myfile.dat":"ImportantFile"}
--Boundary_1_1161035867_1375890821794
Content-Disposition: form-data; name="MyThing"
Content-Type: application/json
{"Id":123,"Name":"myteststring"}
--Boundary_1_1161035867_1375890821794
Content-Type: application/octet-stream
Content-Disposition: form-data; filename="myfile.dat"
mydatagoeshere...
--Boundary_1_1161035867_1375890821794--
.
public class TestObj
{
public long Id { get; set; }
public string Name { get; set; }
}
[Route("/Task", "POST")]
public class TaskRequest : AuthenticatedRequest, IReturn<TaskResponse>
{
public TestObj MyThing { get; set; }
public Dictionary<string, string> MyMap { get; set; }
}

Answer 1

Have you tried setting the properties of your request object using the 'ApiMember' attribute? In particular the 'ParameterType' properties.
/// <summary>
/// Create and upload a new video.
/// </summary>
[Api("Create and upload a new video.")]
[Route("/videos", "POST", Summary = #"Create and upload a new video.",
Notes = "Video file / attachment must be uploaded using POST and 'multipart/form-data' encoding.")]
public class CreateVideo : OperationBase<IVideo>
{
/// <summary>
/// Gets or sets the video title.
/// </summary>
[ApiMember(Name = "Title",
AllowMultiple = false,
DataType = "string",
Description = "Video title. Required, between 8 and 128 characters.",
IsRequired = true,
ParameterType = "form")]
public string Title { get; set; }
/// <summary>
/// Gets or sets the video description.
/// </summary>
[ApiMember(Name = "Description",
AllowMultiple = false,
DataType = "string",
Description = "Video description.",
ParameterType = "form")]
public string Description { get; set; }
/// <summary>
/// Gets or sets the publish date.
/// </summary>
/// <remarks>
/// If blank, the video will be published immediately.
/// </remarks>
[ApiMember(Name = "PublishDate",
AllowMultiple = false,
DataType = "date",
Description = "Publish date. If blank, the video will be published immediately.",
ParameterType = "form")]
public DateTime? PublishDate { get; set; }
}