问JSON到ASP.NET Web API错误：(500)内部服务器错误

EN

    public string SubmitNewIncident(Incident input)
    {
        string response = String.Empty;
        string serialisedJSON = String.Empty;

        input.Type = 0;

        serialisedJSON = JsonConvert.SerializeObject(input);
        string fpath = String.Format(@"C:\dev\serialisedJSONLog_{0}.txt", DateTime.Now.ToString("yyyy-dd-M--HH-mm-ss"));
        System.IO.File.WriteAllText(fpath, serialisedJSON);

        using (WebClient wc = new WebClient())
        {
            wc.Headers[HttpRequestHeader.ContentType] = "application/json";
            try
            {
                response = wc.UploadString(new Uri("http://localhost:25657/api/RaiseNew"), serialisedJSON);
            }
            catch(Exception ex)
            {
                string path = String.Format(@"C:\dev\ErrorLog_{0}.txt", DateTime.Now.ToString("yyyy-dd-M--HH-mm-ss"));
                System.IO.File.WriteAllText(path, ex.ToString());
                throw ex;
            }
        }

        return (response);
    }

public class RaiseNewController : ApiController
{
    // GET api/raisenew
    [HttpGet]
    public HttpStatusCode Get()
    {
        return HttpStatusCode.OK;
    }


    //POST api/raisenew
    [HttpPost]
    public int Post([FromBody] Incident input)
    {
        input.AssignedTo = AssignNewTicket(input.AppID ?? 0);

        return 0;
    }

    System.Net.WebException: The remote server returned an error: (500) Internal Server Error.