通过 Google API 从 ASP.NET 应用程序发送电子邮件

问：

因此，在过去的 2 年里，我一直在通过 GmailService 从我的 .NET WebApp 发送电子邮件，现在它突然停止工作。这是我发送电子邮件的一段代码。

它断了

var renew = 凭据。GetAccessTokenForRequestAsync（）。结果;

出现以下错误：

{错误：“invalid_grant”， 描述：“错误的请求”， URI：“”}

var tokenResponse = new TokenResponse { RefreshToken = sendData.refreshToken };
UserCredential credential = new UserCredential(new ForceOfflineGoogleAuthorizationCodeFlow(
        new GoogleAuthorizationCodeFlow.Initializer
        {
            ClientSecrets = new ClientSecrets
            {
                ClientId = sendData.clientID,
                ClientSecret = sendData.clientSecret
            },
            Scopes = Scopes
        }
        ),
        "me",
        tokenResponse);

var renew = credential.GetAccessTokenForRequestAsync().Result;

// Create service
var service = new GmailService(new BaseClientService.Initializer()
{
    ApplicationName = "MySuperNonWorkingApplication",
    HttpClientInitializer = credential,
});

var message = CreateRawMessageSystemNet(sendData.sendToAddresses,sendData.subject,sendData.body,sendData.email,sendData.emailDisplayName,sendData.attachments);

var result = service.Users.Messages.Send(new Message
{
    Raw = message
}, "me").Execute();

对于UserCredential IAuthorizationCodeFlow参数，我使用的是类

internal class ForceOfflineGoogleAuthorizationCodeFlow : GoogleAuthorizationCodeFlow
{
    public ForceOfflineGoogleAuthorizationCodeFlow(GoogleAuthorizationCodeFlow.Initializer initializer) : base(initializer) { }

    public override AuthorizationCodeRequestUrl CreateAuthorizationCodeRequest(string redirectUrl)
    {
        return new GoogleAuthorizationCodeRequestUrl(new Uri(AuthorizationServerUrl))
        {
            ClientId = ClientSecrets.ClientId,
            Scope = string.Join(" ", Scopes),
            RedirectUri = redirectUrl,
            AccessType = "offline",
            ApprovalPrompt = "force"
        };
    }
}

如果在发送时想知道对象凭据的内容，如下所示： Scopes 变量为“https://mail.google.com/"

提前非常感谢！