What does HttpResponseMessage return as Json

Question

I have a basic question about basics on Web Api. FYI, I have checked before but could not found what I was looking for.

I have a piece of code as described below these lines. Just like any other Method in general terms my method called: Post, it has to return something,a JSON for example, How do I do that. Specifically, what am I supposed to write after the word " return " in order to get the 3 fields( loginRequest.Username,loginRequest.Password,loginRequest.ContractItemId ) as Json. Coments: Do not worry about username,password and contractID are in comments, I do get their value in my LinQ. It's just the return whta I nened now, greetings to all who would like to throw some notes about this.

    [System.Web.Http.HttpPost]
    public HttpResponseMessage Post(LoginModel loginRequest)
    {
        //loginRequest.Username = "staw_60";
        //loginRequest.Password = "john31";
        //loginRequest.ContractItemId = 2443;

      try
        {
           Membership member =
                (from m in db.Memberships
                 where
                     m.LoginID == loginRequest.Username 
                 && m.Password == loginRequest.Password 
                 && m.ContractItemID == loginRequest.ContractItemId
                 select m).SingleOrDefault();   
        }
       catch (Exception e)
       {
            throw new Exception(e.Message);
       }

      return ???;      
    }

Answer 1

Try this:

HttpResponseMessage response = new HttpResponseMessage();
response.Content = new ObjectContent<Response>(
        new Response() { 
                        responseCode = Response.ResponseCodes.ItemNotFound 
                       }, 
                       new JsonMediaTypeFormatter(), "application/json");

or just create another response from Request object itself.

return Request.CreateResponse<Response>(HttpStatusCode.OK, 
      new Response() { responseCode = Response.ResponseCodes.ItemNotFound })

You can also turn all your response types to JSON by updating the HttpConfiguration(Formatter.Remove) just remove the default xml serialization and put JSON.