The problem you are experiencing is similar to this question: Google drive API to C#
You can no longer log into Google Spreadsheets with the old user credentials (username/password only). You need to use OAuth 2.0 now (which requires you to create an app and credentials at console.developers.google.com).
You can use the example below for the authentication logic, and use the logic in the logic found in this question to actually manipulate the file:
Accessing Google Spreadsheets with C# using Google Data API
Here is my answer to the linked question in case it gets deleted in the future:
This example requires you to use the following nuget packages and their dependencies:
- Google.GData.Spreadsheets
Also, you must go to https://console.developers.google.com and register your application and create credentials for it so you can enter your CLIENT_ID and CLIENT_SECRET.
This is the documentation I used to put together this example: https://developers.google.com/google-apps/spreadsheets/
using System;
using System.Windows.Forms;
using Google.GData.Client;
using Google.GData.Spreadsheets;
namespace ConsoleApplication4
{
class Program
{
static void Main(string[] args)
{
string CLIENT_ID = "YOUR_CLIENT_ID";
string CLIENT_SECRET = "YOUR_CLIENT_SECRET";
string SCOPE = "https://spreadsheets.google.com/feeds https://docs.google.com/feeds";
string REDIRECT_URI = "urn:ietf:wg:oauth:2.0:oob";
OAuth2Parameters parameters = new OAuth2Parameters();
parameters.ClientId = CLIENT_ID;
parameters.ClientSecret = CLIENT_SECRET;
parameters.RedirectUri = REDIRECT_URI;
parameters.Scope = SCOPE;
string authorizationUrl = OAuthUtil.CreateOAuth2AuthorizationUrl(parameters);
MessageBox.Show(authorizationUrl);
Console.WriteLine("Please visit the URL in the message box to authorize your OAuth "
+ "request token. Once that is complete, type in your access code to "
+ "continue...");
parameters.AccessCode = Console.ReadLine();
OAuthUtil.GetAccessToken(parameters);
string accessToken = parameters.AccessToken;
Console.WriteLine("OAuth Access Token: " + accessToken);
GOAuth2RequestFactory requestFactory =
new GOAuth2RequestFactory(null, "MySpreadsheetIntegration-v1", parameters);
SpreadsheetsService service = new SpreadsheetsService("MySpreadsheetIntegration-v1");
service.RequestFactory = requestFactory;
SpreadsheetQuery query = new SpreadsheetQuery();
SpreadsheetFeed feed = service.Query(query);
// Iterate through all of the spreadsheets returned
foreach (SpreadsheetEntry entry in feed.Entries)
{
// Print the title of this spreadsheet to the screen
Console.WriteLine(entry.Title.Text);
}
Console.ReadLine();
}
}
}