Question

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using Google.Apis.Gmail.v1.Data;
using Google.Apis.Gmail.v1;
using Google.Apis.Gmail;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.Upload;
using System.Threading;
using System.IO;

namespace Google_Gmail
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();

            Task task = new Task(ListLabels());
            task.Start();
            task.Wait();
        }

        public async Task ListLabels()
        {

            UserCredential credential;
            using (var stream = new FileStream("client_secrets_desktop.json", FileMode.Open, FileAccess.Read))
            {
                credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(GoogleClientSecrets.Load(stream).Secrets,
                    new[] { GmailService.Scope.GmailReadonly },
                    "user", CancellationToken.None);
            }

            var service = new GmailService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = credential,
                ApplicationName = "Gmail Test",
            });

            try
            {
                ListLabelsResponse response = service.Users.Labels.List("me").Execute();
                foreach (Google.Apis.Gmail.v1.Data.Label label in response.Labels.OrderBy(p => p.Name))
                {
                    Console.WriteLine(label.Id + " - " + label.Name);
                }
            }
            catch (Exception e)
            {
                Console.WriteLine("An error occurred: " + e.Message);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
    }
}

我想从我的Gmail帐户中获取所有电子邮件，并将其列在listBox中。我不确定如何使用异步任务方法。我如何在构造函数中调用它？

我收到错误：

错误2参数1：无法转换为System.Threading.Tasks.Task＆＃39;到＆＃39; System.Action＆＃39;

Answer 1

我想知道你为什么这样做，你可以这样称呼：

 public async void Start()
 {
     Task task = ListLabels().ContinueWith(task1 =>
     {
         //control returns to here
     }, TaskScheduler.FromCurrentSynchronizationContext());
 }

并从表单的构造函数中调用此start方法。

我如何使用异步任务方法？

1 个答案: