title: servicestack deserializing JSON in query string variable
body: <p>in the rest service i am emulating the same as another product, json is GET/POSTed in web form or query string parameters.</p>
  
  <p>My request DTO has another DTO object as a property for the json</p>
  
  <p>I can add a RequestFilter to deserialize the form parameters if it is POSTed, but if GET is used with json in a query variable the service stack code will throw an "KeyValueDataContractDeserializer: Error converting to type" exception in StringMapTypeDeserializer.</p>
  
  <p>In StringMapTypeDeserializer it gets a parse function for the properties of the DTO.  Is there anyway of adding something to JsvReader.GetParseFn(propertyType); to handle the de-serialization of my JSON?</p>
  
  <p>Or some other way of adding parsing for this query parameter?  without doing a custom handler.</p>
  
  <p>thanks</p>