Deserializing json from client in json.net 3.5b2 in vb.net

StackOverflow https://stackoverflow.com/questions/489723

  •  20-08-2019
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Question

I have a test case of a problem I'm having, basically I create a json object on the server and provide it back to an AJAX called made on the client side. That works fine, however, when I try to send it back and deserialize it server side I get the following exception:

No parameterless constructor defined for type of 'System.String'.

System.MissingMethodException 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.Serialization.ObjectConverter.ConvertObjectToType(Object o, Type type, JavaScriptSerializer serializer) at System.Web.Script.Services.WebServiceMethodData.StrongTypeParameters(IDictionary2 rawParams) at System.Web.Script.Services.WebServiceMethodData.CallMethodFromRawParams(Object target, IDictionary2 parameters) at System.Web.Script.Services.RestHandler.InvokeMethod(HttpContext context, WebServiceMethodData methodData, IDictionary2 rawParams) at System.Web.Script.Services.RestHandler.ExecuteWebServiceCall(HttpContext context, WebServiceMethodData methodData)

Default.aspx

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>
    <script src="http://www.json.org/json2.js" type="text/javascript"></script>
    <script src="http://code.jquery.com/jquery-latest.pack.js" type="text/javascript" ></script>
    <script type="text/javascript">
        $(document).ready(function(){
            $.theDate = {};
            $("#Button1").click(function(){
                $.ajax({
                    type: 'POST',
                    url: 'default.aspx/getDate',
                    data: '{}',
                    contentType: 'application/json; charset=utf-8',
                    dataType: 'json',
                    success: function(json){
                        var date = eval("("+json.d+")");
                        $.theDate = date;
                        var pdate = eval("("+json.d.replace(/"\\\/Date\(([0-9]+)[0-9-]+\)\\\/"/gi, 'new Date(parseInt($1,10))')+")");
                        $("#now").val(date.now);
                        $("#pnow").val(pdate.now);
                        $("#strnow").val(date.strnow);
                    },
                    error: function(xmlhr, status, err){
                        console.error(arguments);
                        var response = eval("("+xmlhr.responseText+")");
                        console.log(response);
                    }
                });
            });

            $("#Button2").click(function(){
                var json = JSON.stringify($.theDate);
                json = '{"json":'+json+'}';
                $.ajax({
                    type:'POST',
                    url:'default.aspx/deserialize',
                    data: json,
                    contentType:'application/json; charset=utf-8',
                    dataType: 'json',
                    success: function(json){
                        var date = eval("("+json.d+")");
                        console.log(date);
                    },
                    error: function(xmlhr, status, err){
                        console.error(arguments);
                        var response = eval("("+xmlhr.responseText+")");
                        console.log(response);
                    }
                });
            });
        });
    </script>

</head>
<body>
    <form id="form1" runat="server">
    <div>
        <input id="Button1" type="button" value="Get Date" /><br />
        date.now: <input type="text" id="now" value="" style="width:20em" /><br />
        date.now processed: <input type="text" id="pnow" value="" style="width:30em"><br />
        date.strnow: <input type="text" id="strnow" value=""  style="width:20em"/>
        <input id="Button2" type="button" value="Send Date" /><br />
    </div>
    </form>
</body>
</html>

Default.aspx.vb

Imports System.Web.Services
Imports Newtonsoft.Json

Partial Class _Default
    Inherits System.Web.UI.Page

    Private Class _date
        <JsonProperty()> Public now As New Date
        <JsonProperty()> Public strnow As String
        Public Sub New()
            now = Date.Today
            strnow = Date.Today.ToLongDateString
        End Sub
    End Class

    <WebMethod()> Public Shared Function getDate() As String
        Dim theDate As New _date
        Dim strJson As String

        strJson = JsonConvert.SerializeObject(theDate)

        Return strJson
    End Function

    <WebMethod()> Public Shared Function deserialize(ByVal json As String) As String
        Dim newDate As _date
        Try
            newDate = JsonConvert.DeserializeObject(json, GetType(_date))
            Return "{""done"":true}"
        Catch ex As Exception
            Throw ex
        End Try
    End Function
End Class

I'd greatly appreciate help on what I'm doing wrong here. Thanks in advance.

Was it helpful?

Solution

Had to change 

Private Class _date

to 

Public Class _date

and 

<WebMethod()> Public Shared Function deserialize(ByVal json As String) As String

to 

<WebMethod()> Public Shared Function deserialize(ByVal json As _date) As String
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