Gmail api .Net使用访问令牌发送消息

using Google.Apis.Auth.OAuth2;
using Google.Apis.Gmail.v1;
using Google.Apis.Gmail.v1.Data;
using Google.Apis.Services;
using System;
using System.IO;
using System.Threading;

namespace GmailApiExample
{
    class Program
    {
        static void Main(string[] args)
        {
            // 客户端ID和客户端密钥
            string clientId = "YOUR_CLIENT_ID";
            string clientSecret = "YOUR_CLIENT_SECRET";

            // 用户授权范围
            string[] scopes = { GmailService.Scope.GmailCompose, GmailService.Scope.GmailSend };

            // 用户凭据文件路径
            string credentialsPath = "credentials.json";

            // 创建用户凭据
            UserCredential credential;

            using (var stream = new FileStream(credentialsPath, FileMode.Open, FileAccess.Read))
            {
                credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                    GoogleClientSecrets.Load(stream).Secrets,
                    scopes,
                    "user",
                    CancellationToken.None).Result;
            }

            // 创建Gmail服务
            var service = new GmailService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = credential,
                ApplicationName = "Gmail API .NET Example"
            });

            // 创建消息
            var message = new Message()
            {
                Raw = Base64UrlEncode(CreateEmailMessage("sender@example.com", "recipient@example.com", "Subject", "Message body"))
            };

            // 发送消息
            service.Users.Messages.Send(message, "me").Execute();

            Console.WriteLine("Message sent successfully.");
        }

        // 创建电子邮件消息
        private static string CreateEmailMessage(string sender, string recipient, string subject, string body)
        {
            var emailMessage = new System.Net.Mail.MailMessage(sender, recipient, subject, body);
            var memoryStream = new MemoryStream();
            emailMessage.Save(memoryStream);
            return Convert.ToBase64String(memoryStream.ToArray());
        }

        // Base64 URL编码
        private static string Base64UrlEncode(string input)
        {
            var inputBytes = System.Text.Encoding.UTF8.GetBytes(input);
            return Convert.ToBase64String(inputBytes)
                .Replace('+', '-')
                .Replace('/', '_')
                .Replace("=", "");
        }
    }
}