(Mono C#) Automatically Refresh Token for 401 Unauthorized

Demonstrates how to automatically refresh an access token (without user interaction) when the token expires and a 401 Unauthorized response is received.

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

string tokenFilePath = "qa_data/tokens/googleCalendar.json";

// Get our current access token.
Chilkat.JsonObject jsonToken = new Chilkat.JsonObject();
bool success = jsonToken.LoadFile(tokenFilePath);
if (jsonToken.HasMember("access_token") == false) {
    Debug.WriteLine("No access token found.");
    return;
}

Chilkat.Http http = new Chilkat.Http();
http.AuthToken = jsonToken.StringOf("access_token");

string jsonResponse = http.QuickGetStr("https://www.googleapis.com/calendar/v3/users/me/calendarList");
if (http.LastMethodSuccess != true) {

    if (http.LastStatus != 401) {
        Debug.WriteLine(http.LastErrorText);
        Debug.WriteLine("----");
        Debug.WriteLine(http.LastResponseBody);
        return;
    }

    // The access token must've expired. 
    // Refresh the access token and then retry the request.
    Chilkat.OAuth2 oauth2 = new Chilkat.OAuth2();

    oauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token";

    // Replace these with actual values.
    oauth2.ClientId = "GOOGLE-CLIENT-ID";
    oauth2.ClientSecret = "GOOGLE-CLIENT-SECRET";

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

    // Send the HTTP POST to refresh the access token..
    success = oauth2.RefreshAccessToken();
    if (success != true) {
        Debug.WriteLine(oauth2.LastErrorText);
        return;
    }

    // The response contains a new access token, but we must keep
    // our existing refresh token for when we need to refresh again in the future.
    jsonToken.UpdateString("access_token",oauth2.AccessToken);

    // Save the new JSON access token response to a file.
    Chilkat.StringBuilder sbJson = new Chilkat.StringBuilder();
    jsonToken.EmitCompact = false;
    jsonToken.EmitSb(sbJson);
    sbJson.WriteFile(tokenFilePath,"utf-8",false);

    Debug.WriteLine("OAuth2 authorization granted!");
    Debug.WriteLine("New Access Token = " + oauth2.AccessToken);

    // re-try the original request.
    http.AuthToken = oauth2.AccessToken;
    jsonResponse = http.QuickGetStr("https://www.googleapis.com/calendar/v3/users/me/calendarList");
    if (http.LastMethodSuccess != true) {
        Debug.WriteLine(http.LastErrorText);
        return;
    }

}

Debug.WriteLine(jsonResponse);
Debug.WriteLine("-----------------------------");