How to login to Google Calendar without OAuth2? - vb.net

Question

SUMMARY
I have a Vb.net application (Windows form) and I need to manage google calendar for any of software user. I thought of having the user access directly from the program and not authenticate himself for every operation on the calendar
I tried OAuth2 method but is not user friendly. I must login directly from the app and without json files.
WHAT I TRIED
I'm developing software with integrated Google Calendar.
I'm not a Google API expert, so by searching a bit on the web, I managed to authenticate using the credentials.json file that directly creates Google.
At the moment, the software works like this: I press the "Login" button; automatically opens the Google login page in the browser; I enter email and password on the official Google login page; I access; I manually close the browser page; I go back to the program where a msgbox warns me of successful authentication.
Public scopes As IList(Of String) = New List(Of String)()
Public service As CalendarService
Function LoginGoogle()
scopes.Add(CalendarService.Scope.Calendar)
Dim credential As UserCredential
If Directory.Exists("C:\credentials") Then
Try
Directory.Delete("c:\credentials", True)
Catch
MsgBox("Error! Can't delete folder 'credentials'")
End Try
Using stream As New FileStream("credentials.json", FileMode.Open, FileAccess.Read)
credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
GoogleClientSecrets.Load(stream).Secrets, scopes, "user", CancellationToken.None,
New FileDataStore("c:\credentials")).Result
End Using
Dim initializer As New BaseClientService.Initializer()
initializer.HttpClientInitializer = credential
initializer.ApplicationName = "Carpedia" ' app's name
service = New CalendarService(initializer)
Return 0
Else
Using stream As New FileStream("credentials.json", FileMode.Open, FileAccess.Read)
credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
GoogleClientSecrets.Load(stream).Secrets, scopes, "user", CancellationToken.None,
New FileDataStore("c:\credentials")).Result
End Using
Dim initializer As New BaseClientService.Initializer()
initializer.HttpClientInitializer = credential
initializer.ApplicationName = "Carpedia" ' app's name
service = New CalendarService(initializer)
Return 0
End If
End Function
WHAT I WOULD LIKE
I would like to create a form where to enter email and password; click on the login button; log in automatically without using the browser.
Example: https://youtu.be/FW9_gCD8vVg?t=15 (minute 0:18)
How can I do?
Thanks in advance.

Answer 1

Logging in with username and password though your application is called client login. This was shut down by google in 2015.
In order to access user data you must have the permission of the user to do this. The only way for you to get the permission of the user is to use OAuth2. There is no other option for you to do this. As you can see the google calendar api documentation mentions only oauth2 for accessing private user data.
You appear to already be using the Google APIs .net client library which is the best way i know of to authenticate a user in a windows application.