Get "Invalid web service call, missing value for parameter" error when calling a web service method using jQuery

Question

This is my aspx file code:

var DTO = { "'productCategoryId'": "'10'" };
$.ajax({
 type: "GET",
 url: "/WebService/DsmWebServices.asmx/GetProductSubCategory",
 data: DTO,
 contentType: "application/json; charset=utf-8",
 dataType: "json",
 success: function (msg) {
  window.alert("success");
 },
 error: function (msg) {
 }
});

This is my web service method:

[WebMethod,ScriptMethod(UseHttpGet=true)]
public bool GetProductSubCategory(int productCategoryId)
{
 //do some stuff
 return true;
}

The problem is that the jQuery function fails with the following error:

{"Message":"Invalid web service call, missing value for parameter:
\u0027productCategoryId\u0027.","StackTrace":"   at System.Web.Script.Services.WebServiceMethodData.CallMethod(Object target, IDictionary`2 parameters)\r\n   at
System.Web.Script.Services.WebServiceMethodData.CallMethodFromRawParams(Object target, IDictionary`2 parameters)\r\n   at
System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams)\r\n   at
System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)","ExceptionType":"System.InvalidOperationException"}

By using Firebug, the URL jQuery requested was

http://192.168.1.100:8888/WebService/DsmWebServices.asmx/GetProductSubCategory?%27productCategoryId%27=%2710%27

Answer 1

you have to use "post" for the type in your ajax call. Also, the data passed to your web service needs to be a json string. Not a json object. Take a look at the stringify method for the json2 library:

http://www.json.org/js.html