异步编程模型

class Program
    {
        static void Main(string[] args)
        {
            var func = new Func<string, string>(i => { return i + "i can fly"; });

            var state = func.BeginInvoke("yes,", Callback, func);

            Console.Read();
        }

        static void Callback(IAsyncResult async)
        {
            var result = async.AsyncState as Func<string, string>;

            Console.WriteLine(result.EndInvoke(async));
        }
    }

class Program
    {
        static void Main(string[] args)
        {
            var func = new Func<string, string>(i =>
            {
                return i + "i can fly";
            });

            Task<string>.Factory.FromAsync(func.BeginInvoke, func.EndInvoke, "yes,", null).ContinueWith
                (i =>
                {
                    Console.WriteLine(i.Result);
                });

            Console.Read();
        }
    }

static void Main(string[] args)
        {
            var path = "C://1.txt";

            FileStream fs = new FileStream(path, FileMode.Open);

            FileInfo info = new FileInfo(path);

            byte[] b = new byte[info.Length];

            var asycState = fs.BeginRead(b, 0, b.Length, (result) =>
            {
                var file = result.AsyncState as FileStream;

                Console.WriteLine("文件内容：{0}", Encoding.Default.GetString(b));

                file.Close();

            }, fs);

            Console.WriteLine("我是主线程，我不会被阻塞！");

            Console.Read();
        }

static void Main(string[] args)
        {
            var path = "C://1.txt";

            FileStream fs = new FileStream(path, FileMode.Open);

            FileInfo info = new FileInfo(path);

            byte[] b = new byte[info.Length];

            Task<int>.Factory.FromAsync(fs.BeginRead, fs.EndRead, b, 0, b.Length, null, TaskCreationOptions.None)
                .ContinueWith
                (i =>
                {
                    Console.WriteLine("文件内容：{0}", Encoding.Default.GetString(b));
                });

            Console.WriteLine("我是主线程，我不会被阻塞！");

            Console.Read();
        }

class Program
    {
        static byte[] b;

        static void Main()
        {
            string[] array = { "C://1.txt", "C://2.txt", "C://3.txt" };

            List<Task<string>> taskList = new List<Task<string>>(3);

            foreach (var item in array)
            {
                taskList.Add(ReadAsyc(item));
            }

            Task.Factory.ContinueWhenAll(taskList.ToArray(), i =>
            {
                string result = string.Empty;

                //获取各个task返回的结果
                foreach (var item in i)
                {
                    result += item.Result;
                }

                //倒序
                String content = new String(result.OrderByDescending(j => j).ToArray());

                Console.WriteLine("倒序结果："+content);
            });

            Console.WriteLine("我是主线程，我不会被阻塞");

            Console.ReadKey();
        }

        //异步读取
        static Task<string> ReadAsyc(string path)
        {
            FileInfo info = new FileInfo(path);

            byte[] b = new byte[info.Length];

            FileStream fs = new FileStream(path, FileMode.Open);

            Task<int> task = Task<int>.Factory.FromAsync(fs.BeginRead, fs.EndRead, b, 0, b.Length, null, TaskCreationOptions.None);

            //返回当前task的执行结果
            return task.ContinueWith(i =>
            {
                return i.Result > 0 ? Encoding.Default.GetString(b) : string.Empty;
            }, TaskContinuationOptions.ExecuteSynchronously);
        }
    }

class Program
    {
        static void Main(string[] args)
        {
            WebClient client = new WebClient();

            client.DownloadFileCompleted += new System.ComponentModel.AsyncCompletedEventHandler(client_DownloadFileCompleted);

            client.DownloadFileAsync(new Uri("http://imgsrc.baidu.com/baike/abpic/item/6a600c338744ebf844a0bc74d9f9d72a6159a7ac.jpg"),
                                   "1.jpg", "图片下完了，你懂的！");

            Console.WriteLine("我是主线程，我不会被阻塞！");
            Console.Read();
        }

        static void client_DownloadFileCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
        {
            Console.WriteLine("\n" + e.UserState);
        }
    }

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Threading.Tasks;
using System.Net;
using System.ComponentModel;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main()
        {
            var downloadTask = DownLoadFileInTask(
                    new Uri(@"http://www.7720mm.cn/uploadfile/2010/1120/20101120073035736.jpg")
                    , "C://1.jpg");

            downloadTask.ContinueWith(i =>
            {
                Console.WriteLine("图片:" + i.Result + "下载完毕！");
            });

            Console.WriteLine("我是主线程，我不会被阻塞!");

            Console.Read();
        }

        static Task<string> DownLoadFileInTask(Uri address, string saveFile)
        {
            var wc = new WebClient();

            var tcs = new TaskCompletionSource<string>(address);

            //处理异步操作的一个委托
            AsyncCompletedEventHandler handler = null;

            handler = (sender, e) =>
            {
                if (e.Error != null)
                {
                    tcs.TrySetException(e.Error);
                }
                else
                {
                    if (e.Cancelled)
                    {
                        tcs.TrySetCanceled();
                    }
                    else
                    {
                        tcs.TrySetResult(saveFile);
                    }
                }

                wc.DownloadFileCompleted -= handler;
            };

            //我们将下载事件与我们自定义的handler进行了关联
            wc.DownloadFileCompleted += handler;

            try
            {
                wc.DownloadFileAsync(address, saveFile);
            }
            catch (Exception ex)
            {
                wc.DownloadFileCompleted -= handler;

                tcs.TrySetException(ex);
            }

            return tcs.Task;
        }
    }
}

原文地址：https://www.cnblogs.com/liuqifeng/p/9149841.html