JavaScriptSerializer - Invalid JSON Primitive - json

Question

Hello I am creating Desktop App I try to get my table show in my datagrid with source from remote sql server using PHP.
my PHP code to connecting and get the table values
<?php
include "koneksi.php";
$noresi = htmlspecialchars($_POST['NO_RESI']);
if($noresi=="") {
$rs = mysqli_query("SELECT * FROM CekResi");
}else {
$rs = mysqli_query("SELECT * FROM CekResi WHERE NO_RESI='$noresi'");
}
$rows = array();
while($row = mysqli_fetch_object($rs)){
array_push($rows, $row);
}
echo json_encode($rows);
?>
then with desktop app button i did this for showing to my datagrid
Imports System.Web.Script.Serialization
Private Sub btnTAMPILKAN_Click(sender As Object, e As EventArgs) Handles btnTAMPILKAN.Click
Dim WF As New System.Collections.Specialized.NameValueCollection
Dim Server As New System.Uri("http://mywebsite.com/resiapp/resi_view.php") 'URL File PHP
Dim WC As New Net.WebClient
Me.Cursor = Cursors.WaitCursor
Try
WF.Clear()
WF.Add("noresi", txtNORESI.Text.Trim())
Dim RV() As Byte = WC.UploadValues(Server, "POST", WF)
Dim JsonText As String = System.Text.Encoding.ASCII.GetString(RV)
Dim JSS As New JavaScriptSerializer
Dim NomorResi = JSS.Deserialize(Of List(Of KolomResiClass))(JsonText)
Dim BS As New BindingSource
BS.DataSource = NomorResi
dgCEKRESI.AutoGenerateColumns = True
dgCEKRESI.DataSource = BS
Me.Cursor = Cursors.Default
Catch ex As Exception
Me.Cursor = Cursors.Default
MessageBox.Show(ex.Message, "Informasi", MessageBoxButtons.OK, MessageBoxIcon.Warning)
End Try
End Sub
trying to Deserialize my class here
Public Class KolomResiClass
Public Property tgl_pckp As String
Public Property noresi As String
Public Property nama_cust As String
Public Property kota_pckp As String
Public Property kota_tjn As String
Public Property koli As String
Public Property berat As String
Public Property status As String
Public Property tgl_trm As String
Public Property vendor As String
Public Property rincian_cst As String
Public Property marketing As String
Public Property cost As String
Public Property inv_cust As String
Public Property margin As String
End Class
and always got error Invalid JSON Primitive
The error come when I click the button btnTAMPILKAN
Please help I really want to know where is my mistakes.