Error reading JArray from JsonReader VB.net

Question

where does it go wrong? my coding

Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq
Imports System.Net
Public Class DigiposAJA       

    Private Sub CekPaket()
        Dim json As String = (New WebClient).DownloadString("http://192.168.101.1:100/list_product?username=SIP12&category=ROAMING&to=0811&payment_method=LINKAJA&json=1")
        Dim jarr As JArray = Linq.JArray.Parse(json)
        Dim sKatagori As String



        For Each jtk As JToken In jarr
            sKatagori = jtk.SelectToken("kategori")

            DgvDigipos.Rows.Add()
            DgvDigipos.Rows(DgvDigipos.Rows.Count - 1).Cells("DgvKategori").Value = sKatagori
        Next
    End Sub

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        CekPaket()
    End Sub
End Class

after I debug the result is an error like this.

Newtonsoft.Json.JsonReaderException: 'Error reading JArray from JsonReader. Current JsonReader item is not an array: StartObject. Path '', line 1, position 1.'

Can you help me to get a great result

Answer 1

Most likely this is a result of your call to the web service not returning the result you expect.

This is actually a good example of the benefits of separation of concerns and strongly typed objects. Your sub CekPaket should be broken down into 3 parts. 1) get the string. This should be a function and should use some sort of configuration to get the end point and have appropriate guards for failure, 2) parse the string into a strongly typed object (IEnumerable of whatever), this should validation to make sure that the input is good. You might want to make this function public for easy testing. And finally 3) bind your results to your UI. It looks like you are doing this part by hand, whenever possible you should allow the frame work to do this for you by providing a data source and a template for the display.