ServiceStack uses the JSV-Format (JSON without quotes) to parse QueryStrings.

JSV lets you embed deep object graphs in QueryString as seen this example url:

http://www.servicestack.net/ServiceStack.Examples.Host.Web/ServiceStack/Json/
SyncReply/StoreLogs?Loggers=[{Id:786,Devices:[{Id:5955,Type:Panel,
  Channels:[{Name:Temperature,Value:58},{Name:Status,Value:On}]},
  {Id:5956,Type:Tank,TimeStamp:1199303309,
  Channels:[{Name:Volume,Value:10035},{Name:Status,Value:Full}]}]}]

If you want to change the default binding ServiceStack uses, you can register your own Custom Request Binder.

ServiceStack serializes and deserializes your DTOs automatically. If you want to override the default serializers or you want to add a new format, you have to register your own Content-Type:

string contentType = "application/yourformat"; //To override JSON eg, write "application/json"
var serialize = (IRequestContext requestContext, object response, Stream stream) => ...;
var deserialize = (Type type, Stream stream) => ...;

//In AppHost Configure method
//Pass two delegates for serialization and deserialization
this.ContentTypeFilters.Register(contentType, serialize, deserialize);	

The Protobuf-format shows an example of registering a new format whilst the Northwind VCard Format shows an example of creating a custom media type in ServiceStack.

There are 2 ways to deserialize your own custom format, via attaching a custom request binder for a particular service or marking your service with IRequiresRequestStream which will skip auto-deserialization and inject the ASP.NET Request stream instead.

You can register custom binders in your AppHost by using the example below:

base.RequestBinders.Add(typeof(MyRequest), httpReq => ... requestDto);

This gives you access to the IHttpRequest object letting you parse it manually so you can construct and return the strong-typed request DTO manually which will be passed to the service instead.

You can access uploaded files independently of the Request DTO using RequestContext.Files. e.g:

public object Post(MyFileUpload request)
{
    if (this.RequestContext.Files.Length > 0)
    {
        var uploadedFile = this.RequestContext.Files[0];
        uploadedFile.SaveTo(MyUploadsDirPath.CombineWith(file.FileName));
    }
    return HttpResult.Redirect("/");
}

ServiceStack's imgur.servicestack.net example shows how to access the byte stream of multiple uploaded files, e.g:

public object Post(Upload request)
{
    foreach (var uploadedFile in RequestContext.Files
       .Where(uploadedFile => uploadedFile.ContentLength > 0))
    {
        using (var ms = new MemoryStream())
        {
            uploadedFile.WriteTo(ms);
            WriteImage(ms);
        }
    }
    return HttpResult.Redirect("/");
}

Instead of registering a custom binder you can skip the serialization of the request DTO, you can add the IRequiresRequestStream interface to directly retrieve the stream without populating the request DTO.

//Request DTO
public class Hello : IRequiresRequestStream
{
    /// <summary>
    /// The raw Http Request Input Stream
    /// </summary>
    Stream RequestStream { get; set; }
}

You can access raw WCF Message when accessed with the SOAP endpoints in your Service with IHttpRequest.GetSoapMessage() extension method, e.g:

Message requestMsg = base.Request.GetSoapMessage();

To tell ServiceStack to skip Deserializing the SOAP request entirely, add the IRequiresSoapMessage interface to your Request DTO, e.g:

public class RawWcfMessage : IRequiresSoapMessage {
	public Message Message { get; set; }
}

public object Post(RawWcfMessage request) { 
	request.Message... //Raw WCF SOAP Message
}