jQuery DataTables server side processing and ASP.Net

Question

I'm trying to use the server side functionality of the jQuery Datatables plugin with ASP.Net. The ajax request is returning valid JSON, but nothing is showing up in the table.

I originally had problems with the data I was sending in the ajax request. I was getting a "Invalid JSON primative" error. I discovered that the data needs to be in a string instead of JSON serialized, as described in this post: http://encosia.com/2008/06/05/3-mistakes-to-avoid-when-using-jquery-with-aspnet-ajax/. I wasn't quite sure how to fix that, so I tried adding this in the ajax request:

"data": "{'sEcho': '" + aoData.sEcho + "'}"

If the aboves eventually works I'll add the other parameters later. Right now I'm just trying to get something to show up in my table.

The returning JSON looks ok and validates, but the sEcho in the post is undefined, and I think thats why no data is being loaded into the table.

So, what am I doing wrong? Am I even on the right track or am I being stupid? Does anyone ran into this before or have any suggestions?

Here's my jQuery:

$(document).ready(function()
{

    $("#grid").dataTable({
            "bJQueryUI": true,
            "sPaginationType": "full_numbers",
            "bServerSide":true, 
            "sAjaxSource": "GridTest.asmx/ServerSideTest", 
            "fnServerData": function(sSource, aoData, fnCallback) {
               $.ajax({
                    "type": "POST",
                    "dataType": 'json',
                    "contentType": "application/json; charset=utf-8",
                    "url": sSource, 
                    "data": "{'sEcho': '" + aoData.sEcho + "'}",
                    "success": fnCallback
                });
           }
         });


 });

HTML:

<table id="grid">
   <thead>
      <tr>
         <th>Last Name</th>
         <th>First Name</th>
         <th>UserID</th>
       </tr>
    </thead>

    <tbody>
       <tr>
    <td colspan="5" class="dataTables_empty">Loading data from server</td>
       </tr>
    </tbody>
 </table>

Webmethod:

 <WebMethod()> _
Public Function ServerSideTest() As Data


    Dim list As New List(Of String)
    list.Add("testing")
    list.Add("chad")
    list.Add("testing")

    Dim container As New List(Of List(Of String))
    container.Add(list)

    list = New List(Of String)
    list.Add("testing2")
    list.Add("chad")
    list.Add("testing")

    container.Add(list)

    HttpContext.Current.Response.ContentType = "application/json"

    Return New Data(HttpContext.Current.Request("sEcho"), 2, 2, container)

End Function


Public Class Data
Private _iTotalRecords As Integer
Private _iTotalDisplayRecords As Integer
Private _sEcho As Integer
Private _sColumns As String
Private _aaData As List(Of List(Of String))

Public Property sEcho() As Integer
    Get
        Return _sEcho
    End Get
    Set(ByVal value As Integer)
        _sEcho = value
    End Set
End Property

Public Property iTotalRecords() As Integer
    Get
        Return _iTotalRecords
    End Get
    Set(ByVal value As Integer)
        _iTotalRecords = value
    End Set
End Property

Public Property iTotalDisplayRecords() As Integer
    Get
        Return _iTotalDisplayRecords
    End Get
    Set(ByVal value As Integer)
        _iTotalDisplayRecords = value
    End Set
End Property



Public Property aaData() As List(Of List(Of String))
    Get
        Return _aaData
    End Get
    Set(ByVal value As List(Of List(Of String)))
        _aaData = value
    End Set
End Property

Public Sub New(ByVal sEcho As Integer, ByVal iTotalRecords As Integer, ByVal iTotalDisplayRecords As Integer, ByVal aaData As List(Of List(Of String)))
    If sEcho <> 0 Then Me.sEcho = sEcho
    Me.iTotalRecords = iTotalRecords
    Me.iTotalDisplayRecords = iTotalDisplayRecords
    Me.aaData = aaData
End Sub

Returned JSON:

{"__type":"Data","sEcho":0,"iTotalRecords":2,"iTotalDisplayRecords":2,"aaData":[["testing","chad","testing"],["testing2","chad","testing"]]}

Answer 1

I changed the data to

"data": "{'sEcho': '"+ aoData[0].value + "'}",

and it worked. So now the question is how to pass the rest of the data to the webservice. I tried using JSON2 to turn the JSON into a string, but that opened up another can of worms, and is a separate issue.