no parameterless constructor defined for this object when call web service from AJAX

Question

I want to call my web service from JScript using AJAX, and found the error.

the error is:

{Message: "No parameterless constructor defined for type of 'System.String'.",…} ExceptionType: "System.MissingMethodException" Message: "No parameterless constructor defined for type of 'System.String'." StackTrace: " at System.Web.Script.Serialization.ObjectConverter.ConvertDictionaryToObject(IDictionary2 dictionary, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject) ↵ at System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeInternal(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject) ↵ at System.Web.Script.Serialization.ObjectConverter.ConvertObjectToTypeMain(Object o, Type type, JavaScriptSerializer serializer, Boolean throwOnError, Object& convertedObject) ↵ at System.Web.Script.Services.WebServiceMethodData.StrongTypeParameters(IDictionary2 rawParams) ↵ at System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary`2 rawParams) ↵ at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)"

here is my AJAX

function retrieveToken(){var BodyToken = JSON.stringify({
    "userName": "crm"
});
var param1= {
    Token : BodyToken
}

var param2 = JSON.stringify({
    param1
});
$.ajax({
    url: "http://10.23.64.43:8035/iFrameIntegration.asmx/getToken?",
    data: "Token="+JSON.stringify({"userName":"crm"}),
    contentType: "application/json; charset=utf-8",
    type: 'GET',
    success: function (data) {
        alert(data);
    },
    error: function (data) {
        alert("Error");
    }
});}

and here is my web service

public class iFrameIntegration : System.Web.Services.WebService
{

    [WebMethod]
    [ScriptMethod(UseHttpGet = true, ResponseFormat = ResponseFormat.Json)]
    public void getToken(string Token)
    {
        var request = (HttpWebRequest)WebRequest.Create("http://10.23.64.37:8080/ACCMWS/member/SSOInit");
        var DataObject = Token;
        var data = Encoding.ASCII.GetBytes(DataObject);
        request.Method = "POST";
        request.ContentType = "application/json";
        //request.Headers["Content-Type"] = "application/json";
        request.Headers["userId"] = "Svc_CRM";
        request.Headers["loginType"] = "Internal";
        request.Headers["token"] = "54a93982adf51adfb81885ddbbb1874e271605ce";

        try
        {
            request.ContentLength = data.Length;
            Stream dataStream = request.GetRequestStream();
            dataStream.Write(data, 0, data.Length);
            dataStream.Close();
            WebResponse response = request.GetResponse();
            Stream resultStream = response.GetResponseStream();

            StreamReader reader = new StreamReader(resultStream);
            string readerResponse = reader.ReadToEnd();
            var result = JsonConvert.DeserializeObject<RetrieveSSOTokenResult>(readerResponse);
            //return result.data.ssotokenList[0].ssoToken;
            PrintValue(result.data.ssotokenList[0].ssoToken);
        }
        catch(Exception ex)
        {
            ex.Message.ToString();
        }

    }

    private void PrintValue(object obj)
    {
        Context.Response.Write(obj.ToString());
    }
}}

and also here is my class

namespace FWDiFrameIntegration{
public class RetrieveSSOTokenResult
{
    public string status { get; set; }
    public string message { get; set; }
    public Data data { get; set; }
}

public class Data
{
    public Ssotokenlist[] ssotokenList { get; set; }
}

public class Ssotokenlist
{
    public string loginType { get; set; }
    public string userName { get; set; }
    public string userId { get; set; }
    public string ssoToken { get; set; }
    public long expiryTime { get; set; }
}}

please advise

UPDATE.

finally, able to resolved based on Gaurav information. the error comes, because i'm using public void. here is my update web service

[WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string getToken()
    {
        var request = (HttpWebRequest)WebRequest.Create("http://10.23.64.37:8080/ACCMWS/member/SSOInit");
        request.Method = "POST";
        request.ContentType = "application/json";
        request.Headers["userId"] = "Svc_CRM";
        request.Headers["loginType"] = "Internal";
        request.Headers["token"] = "54a93982adf51adfb81885ddbbb1874e271605ce";

        string result = string.Empty;
        try
        {
            using (var streamWriter = new StreamWriter(request.GetRequestStream()))
            {
                string json = "{ \"userName\": \"crm\"}";
                streamWriter.Write(json);
                streamWriter.Flush();
                streamWriter.Close();
            }
            try
            {
                using (var response = request.GetResponse() as HttpWebResponse)
                {
                    if (request.HaveResponse && response != null)
                    {
                        using (var reader = new StreamReader(response.GetResponseStream()))
                        {
                            var resultTokenAwal = reader.ReadToEnd();
                            var resultToken = JsonConvert.DeserializeObject<RetrieveSSOTokenResult>(resultTokenAwal);
                            result = resultToken.data.ssotokenList[0].ssoToken;
                        }
                    }
                }
            }
            catch (WebException e)
            {
                if (e.Response != null)
                {
                    using (var errorResponse = (HttpWebResponse)e.Response)
                    {
                        using (var reader = new StreamReader(errorResponse.GetResponseStream()))
                        {
                            string error = reader.ReadToEnd();
                            result = error;
                        }
                    }

                }
            }
        }
        catch(Exception ex)
        {
            ex.Message.ToString();
        }
        return result;
    }

Answer 1

Ok after little research finally I got it working by changing the method verb to POST instead of GET as we can not(or gets too complicated) send the complex data type in GET requests. Here is code:

 [WebMethod]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public void getToken(object Token)
    {

    }

Here is ajax code:

$.ajax({
            url: "/iFrameIntegration.asmx/getToken",
            data: JSON.stringify({ Token: { userData: 'crm' } }),
            contentType: "application/json; charset=utf-8",
            type: 'POST',
            success: function (data) {
                alert(data);
            },
            error: function (data) {
                alert("Error");
            }
        });