(VB.NET UWP/WinRT) Refresh a Constant Contact OAuth2 Access Token

Refreshes a Constant Contact OAuth2 access token. When an access token expires, HTTPS requests will receive a 401 status response indicating failure. When that happens, your application can run this code to refresh the access token, and then retry the request using the new access token. Refreshing an access token does not need user interaction (i.e. does not need to display a browser to have the user interactive authorize access).

For more information, see https://v3.developer.constantcontact.com/api_guide/server_flow.html#step-5-refresh-the-access-token

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' It is assumed we previously obtained an OAuth2 access token.
' This example loads the JSON access token file 
' saved by this example: Get Constant Contact OAuth2 Access Token

Dim jsonToken As New Chilkat.JsonObject
Dim success As Boolean = jsonToken.LoadFile("qa_data/tokens/constantContact.json")
If (success <> True) Then
    Debug.WriteLine("Failed to load constantContact.json")
    Exit Sub
End If


' The access token JSON looks like this:

' {
'   "access_token": "aEr4czHReESHUGcc2LRknzsMxUbW",
'   "refresh_token": "s2qH27ikM7r3Ia0LrZGDOIgKw0bubUotBdJ7fTtc7y",
'   "token_type": "Bearer"
' }



Dim oauth2 As New Chilkat.OAuth2

oauth2.VerboseLogging = True

oauth2.TokenEndpoint = "https://idfed.constantcontact.com/as/token.oauth2"
oauth2.UseBasicAuth = True
oauth2.UncommonOptions = "OAUTH2_REFRESH_NO_SCOPE"

' Replace these with actual values.
oauth2.ClientId = "CLIENT_KEY"
oauth2.ClientSecret = "CLIENT_SECRET"

' Get the "refresh_token"
oauth2.RefreshToken = jsonToken.StringOf("refresh_token")

Debug.WriteLine("Existing refresh_token: " & oauth2.RefreshToken)

' Send the HTTP POST to refresh the access token..
success = Await oauth2.RefreshAccessTokenAsync()
If (success <> True) Then
    Debug.WriteLine(oauth2.LastErrorText)
    Exit Sub
End If


jsonToken.UpdateString("access_token",oauth2.AccessToken)
jsonToken.UpdateString("refresh_token",oauth2.RefreshToken)

' Save the new JSON access token response to a file.
Dim sbJson As New Chilkat.StringBuilder
jsonToken.EmitCompact = False
jsonToken.EmitSb(sbJson)
sbJson.WriteFile("qa_data/tokens/constantContact.json","utf-8",False)

Debug.WriteLine("OAuth2 token refreshed!")
Debug.WriteLine("New Access Token = " & oauth2.AccessToken)
Debug.WriteLine("New refresh_token: " & oauth2.RefreshToken)