.NET Core C#

Get XOAUTH2 Access Token from Google OAuth 2.0 Authorization Server

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Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server. This is for Server to server applications using Google API's that need an access token. See https://developers.google.com/accounts/docs/OAuth2ServiceAccount .NET Core C#

bool success = false;

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

Chilkat.Http http = new Chilkat.Http();

// --------------------------------------------------------------------------------
// For a step-by-step guide for setting up your Google Workspace service account,
// see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
// --------------------------------------------------------------------------------
// Begin by loading your Google service account key (.p12)
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadPfxFile("c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12","notasecret");
if (success != true) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

// The ISS is your service account email address ending in gserviceaccount.com.
string iss = "chilkatsvc@chilkat25.iam.gserviceaccount.com";

// The scope is always the following string:
string scope = "https://mail.google.com/";

// The sub is your company email address
string oauth_sub = "bob@yourcompany.com";

// The access token is valid for this number of seconds.
int numSec = 3600;

string accessToken = http.G_SvcOauthAccessToken(iss,scope,oauth_sub,numSec,cert);
if (http.LastMethodSuccess != true) {
    Debug.WriteLine(http.LastErrorText);
    return;
}
else {
    Debug.WriteLine("access token: " + accessToken);
}

// The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.