500 Error - JSON object POST to .ASMX webservice

Question

Keep the question here short and sweet. I'm Getting a 500 error when I try and pass a JSON object to an ASMX webservice. Note that if I declare the params as individual variables (eg. int ID, int OrderHeaderID, etc) I do not receive the error. I can't see why the problem is happening, I have successfully passed objects in this manner before, possibly with different syntax but I can't recall.

JS:

var returnHeader = {
    ID: -1,
    OrderHeaderID: parseInt(getQueryStringKey('OrderID')),
    StatusID: 1,
    DeliveryCharge: 0,
    CreatedBy: $('span[id$="lblHidUsername"]').text(),
    ApprovedBy: $('span[id$="lblHidUsername"]').text()
};

$.ajax({
    type: "POST",
    url: 'Order.asmx/SaveReturnHeader',
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    data: JSON.stringify(returnHeader),
    success: function (result) {
        if (result.Status == 'OK') {
            GetReturns();
        }
        else {
            $('#divMessage').show().html(result.Data.Message).addClass('error');
        }
    },
    error: function (x, e) {
        if (x.status == 500) {
            $('#divMessage').show().html('An unexpected server error has occurred, please contact support').addClass('error');
        }
    }
});

Server:

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public object SaveReturnHeader(BEReturnHeader returnHeader)
{
    try
    {
        return new
        {
            Status = "OK",
            Data = ""
        };                
    }
    catch (Exception ex)
    {
        return new
        {
            Status = "ERROR",
            Data = ex
        }; 
    }
}

Object (abbreviated for simplicity):

public int ID ...
public int OrderHeaderID ...
public int StatusID ...
public decimal DeliveryCharge ...
public string CreatedBy  ...
public string ApprovedBy ...

Request Data:

{"ID":-1,"OrderHeaderID":5,"StatusID":1,"DeliveryCharge":0,"CreatedBy":"77777777","ApprovedBy":"77777777"}

Response Headers:

HTTP/1.1 500 Internal Server Error
Date: Mon, 05 Dec 2011 16:38:36 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 2.0.50727
jsonerror: true
Cache-Control: private
Content-Type: application/json
Content-Length: 91

Response Data:

{"Message":"There was an error processing the request.","StackTrace":"","ExceptionType":""}

FIX:

Had to wrap the JSON object so it was recognized on the server:

var params = {
            returnHeader: {
                ...
            }
        };

...
data: JSON.stringify(params),
...

{"returnHeader":{"ID":-1,"OrderHeaderID":5,"StatusID":1,"DeliveryCharge":0,"CreatedBy":"77777777","ApprovedBy":"77777777"}}

Answer 1

You're only passing in the object's properties, not the entire object container. So, the web method is expecting something like this instead:

{returnHeader:{"ID":-1,"OrderHeaderID":5,"StatusID":1,"DeliveryCharge":0,"CreatedBy":"77777777","ApprovedBy":"77777777"}}