未调用PareserError函数

Question

我收到此错误，我不知道如何通过它。我正在尝试执行ajax调用来填充我的数据存储。错误是：

当我这样做时，没有调用Parsererror'function'：

var customStore = new DevExpress.data.CustomStore({
    load: function () {
        return $.ajax({
            url: 'URL/Service/GetCustomers?callback=?fnsuccesscallback',
            crossOrigin: true,
            crossDomain: true,
            jsonp: true,
            type: 'GET',
            dataType: 'jsonp',
            contentType: "application/json; charset=utf-8",

            jsonpCallback: 'fnsuccesscallback',
            async: false,

            success: function (res) {
                console.log("success");
                res = JSON.parse(res);
                console.log("data _" + res);
            },
            error: function (xhr, status, error) {
                console.log(xhr);
                console.log(status);
                console.log(error);
            }
        });
    }
});

var fnsuccesscallback = function (data) {
    alert(data);
};
var gridDataSourceConfiguration = {
    store: customStore
};

此功能的我的服务代码是：

    Function GetCustomers() As Stream Implements IService.GetCustomers

        Try
            Dim Cust As List(Of Customers) = New List(Of Customers)

            Dim SQLSTR As String = ""
            SQLSTR = "Select Code, Name, ID FROM Table"

            Dim ErrorMessage As String = ""
            ErrorMessage = Obj.OpenConnection(SQLServer, UmbrellaDatabase, UserCode, UserPassword)
            If ErrorMessage <> "" Then
                System.Diagnostics.EventLog.WriteEntry("APP", ErrorMessage, EventLogEntryType.Error)
                WebOperationContext.Current.OutgoingResponse.StatusCode = 501
                WebOperationContext.Current.OutgoingResponse.StatusDescription = ErrorMessage


                Return Nothing
            Else
                Dim CustomerDetails As DataSet
                CustomerDetails = tObj.GetDataSQL(SQLSTR)
                If Not CustomerDetails Is Nothing Then
                    CustomerDetails.DataSetName = "Companies"
                    CustomerDetails.Tables(0).TableName = "Companies"
                    Dim CustomerTable As DataTable
                    Dim CustomerRow As DataRow

                    If CustomerDetails.Tables.Count > 0 Then
                        CustomerTable = CustomerDetails.Tables(0)
                        If CustomerTable.Rows.Count > 0 Then

                            Dim i As Integer

                            For i = 0 To CustomerTable.Rows.Count - 1
                                CustomerRow = CustomerTable.Rows(i)
                                Dim CC As New Customers
                                CC.Code = CustomerRow.Item("Code")
                                CC.Name = CustomerRow.Item("Name")
                                CC.InternalID = CustomerRow.Item("InternalID")

                                Cust.Add(CC)


                            Next i
                            ' Serialize the results as JSON
                            Dim serializer As DataContractJsonSerializer = New DataContractJsonSerializer(Cust.GetType())
                            Dim Stream As MemoryStream = New MemoryStream

                            serializer.WriteObject(Stream, Cust)

                            ' Return the results serialized as JSON
                            Dim json As String = Encoding.Default.GetString(Stream.ToArray())

                            Return New MemoryStream(Encoding.UTF8.GetBytes(json))

                            Obj.CloseConnection()
                            WebOperationContext.Current.OutgoingResponse.StatusCode = 200
                            WebOperationContext.Current.OutgoingResponse.StatusDescription = "OK"
                        End If
                    End If

                Else
                    System.Diagnostics.EventLog.WriteEntry("APP", ErrorMessage, EventLogEntryType.Error)

                    WebOperationContext.Current.OutgoingResponse.StatusCode = 501
                    WebOperationContext.Current.OutgoingResponse.StatusDescription = ErrorMessage

                    Cust = Nothing
                    Return Nothing
                End If
            End If



        Catch ex As Exception
            System.Diagnostics.EventLog.WriteEntry("Umbrella Mobile Service", ex.Message, EventLogEntryType.Error)

            WebOperationContext.Current.OutgoingResponse.StatusCode = 501
            WebOperationContext.Current.OutgoingResponse.StatusDescription = ex.Message


            Return Nothing
        End Try
        Dispose()

    End Function

为了发送正确的回调，我的JSON输出应如何在我的服务中显示？为了不显示此错误，我该怎么做？