如何在c# MVC中从Google+登录迁移到Google登录

string clientId = "YOUR_CLIENT_ID";
string redirectUri = "YOUR_REDIRECT_URI";
string authorizationUrl = $"https://accounts.google.com/o/oauth2/v2/auth?client_id={clientId}&redirect_uri={redirectUri}&response_type=code&scope=openid%20email%20profile";

string code = Request.QueryString["code"];
string tokenUrl = "https://accounts.google.com/o/oauth2/token";
string accessToken = "";

using (HttpClient client = new HttpClient())
{
    var tokenResponse = await client.PostAsync(tokenUrl, new StringContent($"code={code}&client_id={clientId}&redirect_uri={redirectUri}&grant_type=authorization_code", Encoding.UTF8, "application/x-www-form-urlencoded"));
    var tokenJson = await tokenResponse.Content.ReadAsStringAsync();
    var tokenData = JsonConvert.DeserializeObject<dynamic>(tokenJson);

    accessToken = tokenData.access_token;
}

string peopleApiUrl = "https://people.googleapis.com/v1/people/me?personFields=names,emailAddresses";
string userInfo = "";

using (HttpClient client = new HttpClient())
{
    client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);

    var userInfoResponse = await client.GetAsync(peopleApiUrl);
    userInfo = await userInfoResponse.Content.ReadAsStringAsync();
}