How to use GetStringAsync in VB.NET - json

Question

I don't really know what I'm going. Trying to gather small pieces of code from the web
I ended up with this:
Imports System.IO
Imports System.Net
Imports Newtonsoft.Json.Linq
Module Module1
Sub Main()
LoadData()
End Sub
Private Async Sub LoadData()
Dim client As New Net.Http.HttpClient()
Dim url = "my url which return json"
Dim uri As New Uri(url)
Dim json As String = Await client.GetStringAsync(uri)
Dim j = JObject.Parse(json)("TIME SERIES INTRADAY")
Dim openPrice = j("1. open").Value(Of Double)
Diagnostics.Debug.WriteLine(openPrice)
Console.ReadLine()
End Sub
End Module
There is no issue when I build but when I run, I get this erroer message when I step on row
Dim json As String = Await client.GetStringAsync(uri)
error code:
The program '[4032] AVT.exe' has exited with code 0 (0x0).
Do you know why this line is returning this error?
Framework 4.5

Answer 1

You won't be able to do top-level Await in a console program. You can still make it work (preserving the Async on LoadData) with the following changes:
Change the signature of LoadData to Private Async Function LoadData() As Task
Change the call in Main to `LoadData.GetAwaiter().GetResult()
This will block in Main which is fine because there is no message loop to support a non-blocking wait. This is only appropriate in a console program, if you were doing this in any other setting your original implementation would have been correct (except that you should always use Async Function ... As Task in preference to Async Sub in any context aside from event handlers).

Answer 2

Yes, you can do this even in a console application.
I suggest you to use an ApplicationContext in order to keep all alive.
Doing as you shows, so, calling your LoadData()
your Main Sub going tasks are:
Enter
(and immediately after)
Exit
.
Take a look on code below to figure out the mechanism that you need to do what you want to do.
Imports System.IO
Imports System.Net
Imports Newtonsoft.Json.Linq
Module Module1
Public Class MyApplicationContext
Inherits ApplicationContext
Private Async Sub LoadData()
Dim client As New Net.Http.HttpClient()
Dim url = "https://stackoverflow.com/questions/59324373/how-to-use-getstringasync-in-vb-net"
Dim uri As New Uri(url)
Dim json As String = Await client.GetStringAsync(uri)
Console.WriteLine(json)
Diagnostics.Debug.WriteLine(json)
'Dim j = JObject.Parse(json)("TIME SERIES INTRADAY")
'Dim openPrice = j("1. open").Value(Of Double)
'Diagnostics.Debug.WriteLine(openPrice)
Console.ReadLine() 'Here is stopped/waiting for user
'Here your application can be stopped after her work
'Application.Exit()
End Sub
Public Sub New()
MyBase.New()
AddHandler Application.ApplicationExit, AddressOf OnApplicationExit
LoadData()
End Sub
Private Sub OnApplicationExit(ByVal sender As Object, ByVal e As EventArgs)
Try
' delete your data here
Catch
End Try
End Sub
End Class
Public Sub Main()
Dim context As MyApplicationContext = New MyApplicationContext()
Application.Run(context)
End Sub
End Module