(.NET Core C#) Google OAuth2 Access Token

Demonstrates how to get a Google OAuth2 access token from a desktop application or script.

Note: This example requires Chilkat v10.1.2 or later.

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// To further clarify, see OAuth 2.0 Authorization Flow

Chilkat.OAuth2 oauth2 = new Chilkat.OAuth2();

// For Google OAuth2, set the listen port equal to the port used
// in the Authorized Redirect URL for the Client ID.
// For example, in this case the Authorized Redirect URL would be http://localhost:55568/
// Your app should choose a port not likely not used by another application.
oauth2.ListenPort = 55568;

oauth2.AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth";
oauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token";

// Replace this with your actual client ID.
oauth2.ClientId = "GOOGLE-CLIENT-ID";

// This is the scope for Google Drive.
// See https://developers.google.com/identity/protocols/googlescopes
// Add the scopes that you need.
oauth2.Scope = "https://www.googleapis.com/auth/drive";

// Begin the OAuth2 authorization code flow.  This returns a URL that should be loaded in a browser.
string url = oauth2.StartAuth();
if (oauth2.LastMethodSuccess != true) {
    Debug.WriteLine(oauth2.LastErrorText);
    return;
}

// Launch the default browser on the system and navigate to the url.
// The LaunchBrowser method was added in Chilkat v10.1.2.
bool success = oauth2.LaunchBrowser(url);
if (success == false) {
    Debug.WriteLine(oauth2.LastErrorText);
    return;
}

// Wait for the interactive user to grant permission in the interactive browser session.
// We'll wait for a max of 90 seconds.
int numMsWaited = 0;
while ((numMsWaited < 90000) && (oauth2.AuthFlowState < 3)) {
    oauth2.SleepMs(100);
    numMsWaited = numMsWaited + 100;
}

// If there was no response from the browser within 90 seconds, then 
// the AuthFlowState will be equal to 1 or 2.
// 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
// 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
// In that case, cancel the background task started in the call to StartAuth.
if (oauth2.AuthFlowState < 3) {
    oauth2.Cancel();
    Debug.WriteLine("No response from the browser!");
    return;
}

// Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
// The possible AuthFlowState values are:
// 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
// 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
// 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
if (oauth2.AuthFlowState == 5) {
    Debug.WriteLine("OAuth2 failed to complete.");
    Debug.WriteLine(oauth2.FailureInfo);
    return;
}

if (oauth2.AuthFlowState == 4) {
    Debug.WriteLine("OAuth2 authorization was denied.");
    Debug.WriteLine(oauth2.AccessTokenResponse);
    return;
}

if (oauth2.AuthFlowState != 3) {
    Debug.WriteLine("Unexpected AuthFlowState:" + Convert.ToString(oauth2.AuthFlowState));
    return;
}

// Save the full JSON access token response to a file.
Chilkat.StringBuilder sbJson = new Chilkat.StringBuilder();
sbJson.Append(oauth2.AccessTokenResponse);
sbJson.WriteFile("qa_data/tokens/_googleDrive.json","utf-8",false);

// The saved JSON response looks like this:

// 	{
// 	 "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtBBBHkZzrwlARkwX6R3O0PCDEzRlfaQ",
// 	 "token_type": "Bearer",
// 	 "expires_in": 3600,
// 	 "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
// 	}
// 
Debug.WriteLine("OAuth2 authorization granted!");
Debug.WriteLine("Access Token = " + oauth2.AccessToken);

// Here is an example showing how to define your OAuth 2.0 Credential in the Google Cloud Console
// Note: Even though your application is technically not a web app, you should still select "Web Application"
// because the Redirect URI is going to http://localhost:55568/ where Chilkat will receive it in a background thread.

//