成功不会调用web服务在ajax调用vb.net中返回的数据

Question

我正在使用ajax来调用vb.net中的web服务。我的web服务被成功调用但是在返回后数据控制直接转到ajax调用的OnError.Also web-service被成功调用但是之后控制直接进入失败方法。我的ajax调用是这样的：

   $.ajax({
            type: "POST",
            url: "../Transactions/WBS_Budget_Dynamic.aspx/GetAllData",
            dataType: "text",
            async: false,
            data: JSON.stringify(obj),

            contentType: "application/json; charset=utf-8",
            error: function (jqXHR, status, err) {
                alert("Local error callback.");
            },

            success: function (data) {

                 alert(JSON.stringify(data.d));
                            :
                            :

我的网络服务撤回了这样的数据：

  dttask = objProjectBL.GetBudgetProcessDetails(ProjNo, Parent, Type, Level, DateTime.Now, DateTime.Now, UserNm, HostNm, SelectType, Report_id)
            Dim serializer As System.Web.Script.Serialization.JavaScriptSerializer = New System.Web.Script.Serialization.JavaScriptSerializer()
            Dim rows As List(Of Dictionary(Of String, Object)) = New List(Of Dictionary(Of String, Object))()


            Dim row As Dictionary(Of String, Object)
            For Each dr As DataRow In dttask.Rows

                row = New Dictionary(Of String, Object)()
                For Each col As DataColumn In dttask.Columns

                    row.Add(col.ColumnName, dr(col))

                Next
                row.Add("ParentId", Parent)

                Dim str As String = dr("Tree_id").ToString()
                Dim count As Integer = str.Split(".").Length - 1
                Dim LevelCount As Integer = count - 1

                row.Add("LevelId", LevelCount.ToString())
                rows.Add(row)
            Next



            Return serializer.Serialize(rows)