Pass multiple parameters into WCF Web API-service

Question

I'm wondering about the behind the scenes magic that's happening when you create a WCF-Web service.

In one old project I got methods that I can call from JavaScript that look like this

[OperationContract]
[WebInvoke(Method = "POST", ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json)]
IEnumerable<Result> SearchObjects(string x, int y, double z);

And this works when I send { "x": "something", "y": 1, "z": 1.5 } from JavaScript.

A couple of months after the creation of that webservice, I found the WCF Web API and tried to make something similar.

Difference was that I created the route in my Global.asax with the HttpServiceHostFactory()

Now when I try to call the method, I get an exception like this

Exception Details: System.InvalidOperationException: The HttpOperationHandlerFactory is unable to determine the input parameter that should be associated with the request message content for service operation 'Invoke_LoginRequest'. If the operation does not expect content in the request message use the HTTP GET method with the operation. Otherwise, ensure that one input parameter either has it's IsContentParameter property set to 'True' or is a type that is assignable to one of the following: HttpContent, ObjectContent1, HttpRequestMessage or HttpRequestMessage1.

And to get it to work, I need to declare the method like this (VB.Net)

Public Function Invoke_LoginRequest(ByVal request As HttpRequestMessage(Of JsonValue)) As HttpResponseMessage(Of String)

But then I need to parse the JsonValue manually. So how does the old version really work? And is there any way I could get that behaviour back?

Best regards Jesper

Answer 1

1) Define a class containing the data that you want to receive, i.e,

public class Model
{
    public string x { get; set; }
    public int y { get; set; }
    public double z { get; set; }
}

2) Define the operation parameter as an ObjectContent<Model>

public HttpResponseMessage Post(ObjectContent<Model> c){
    Model m = c.ReadAs();
    ...
}

HTH Pedro