C# 中的异步编程

一，编写的目的

主要是为了介绍C#中异步编程相关的概念与本人使用的心得总结，对阅读与参考的网络资料进行了整理与归类，记录与明确本人在日常代码中关于异步编程的一些编写习惯与规范。

二、预期读者

熟悉.NET编程，具有.NET代码的阅读与编写基础。

三、异步编程的一些基本概念

四、C# 中的异步编程例子 

  • Task的使用

    1、C# Task详解

    2、C# Task和async/await详解

    3、Task调度器

    4、优雅地使用C#异步

    5、C#同步方法中如何调用异步方法

  • Task.Run和Task.Factory.StartNew

    1、C# Task.Run 和 Task.Factory.StartNew 区别

    2、Task.Run Vs Task.Factory.StartNew

  • 使用 Async 和 Await 的异步编程

    1、async和await详解

    2、核心代码

      1     public class Breakfast
  2     {
  3         /// <summary>
  4         /// 同步版本
  5         /// </summary>
  6         [Benchmark(Baseline = true)]
  7         public void RunV1()
  8         {
  9             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 开始....");
 10             var st = Stopwatch.StartNew();
 11 
 12             Coffee cup = PourCoffee();
 13             PourCoffeeSuccess();
 14 
 15             Egg eggs = FryEggs(2);
 16             FryEggsSuccess();
 17 
 18             Bacon bacon = FryBacon(3);
 19             FryBaconSuccess();
 20 
 21             Toast toast = ToastBread(2);
 22             ApplyButter(toast);
 23             ApplyJam(toast);
 24             ToastBreadSuccess();
 25 
 26             Juice oj = PourOJ();
 27             PourOJSuccess();
 28             Console.WriteLine($"Breakfast is ready!{Environment.NewLine}");
 29             st.Stop();
 30             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 结束，耗时 = {st.ElapsedMilliseconds.ToString("###,###")} 毫秒");
 31         }
 32 
 33         /// <summary>
 34         /// 异步版本，注意 await 关键字
 35         /// </summary>
 36         /// <returns></returns>
 37         [Benchmark]
 38         public async Task RunV2()
 39         {
 40             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 开始....");
 41             var st = Stopwatch.StartNew();
 42 
 43             Coffee cup = PourCoffee();
 44             PourCoffeeSuccess();
 45 
 46             // 异步煎鸡蛋
 47             Egg eggs = await FryEggsAsync(2);
 48             FryEggsSuccess();
 49 
 50             // 异步煎培根
 51             Bacon bacon = await FryBaconAsync(3);
 52             FryBaconSuccess();
 53 
 54             // 异步烤面包
 55             Toast toast = await ToastBreadAsync(2);
 56             ApplyButter(toast);
 57             ApplyJam(toast);
 58             ToastBreadSuccess();
 59 
 60             Juice oj = PourOJ();
 61             PourOJSuccess();
 62 
 63             Console.WriteLine($"Breakfast is ready!{Environment.NewLine}");
 64             st.Stop();
 65             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 结束，耗时 = {st.ElapsedMilliseconds.ToString("###,###")} 毫秒");
 66         }
 67 
 68         [Benchmark]
 69         public async Task RunV3()
 70         {
 71             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 开始....");
 72             var st = Stopwatch.StartNew();
 73 
 74             Coffee cup = PourCoffee();
 75             PourCoffeeSuccess();
 76 
 77             var eggsTask = FryEggsAsync(2);
 78             await eggsTask;
 79             FryEggsSuccess();
 80 
 81             var baconTask = FryBaconAsync(3);
 82             await baconTask;
 83             FryBaconSuccess();
 84 
 85             var toastTask = ToastBreadAsync(2);
 86             var toast = await toastTask;
 87             ApplyButter(toast);
 88             ApplyJam(toast);
 89             ToastBreadSuccess();
 90 
 91             Juice oj = PourOJ();
 92             PourOJSuccess();
 93 
 94             Console.WriteLine($"Breakfast is ready!{Environment.NewLine}");
 95             st.Stop();
 96             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 结束，耗时 = {st.ElapsedMilliseconds.ToString("###,###")} 毫秒");
 97         }
 98 
 99         [Benchmark]
100         public async Task RunV4()
101         {
102             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 开始....");
103             var st = Stopwatch.StartNew();
104 
105             Coffee cup = PourCoffee();
106             PourCoffeeSuccess();
107 
108             var eggsTask = FryEggsAsync(2);
109             var baconTask = FryBaconAsync(3);
110             var toastTask = ToastBreadAsync(2);
111 
112             await eggsTask;
113             FryEggsSuccess();
114 
115             await baconTask;
116             FryBaconSuccess();
117 
118             var toast = await toastTask;
119             ApplyButter(toast);
120             ApplyJam(toast);
121             ToastBreadSuccess();
122 
123             Juice oj = PourOJ();
124             PourOJSuccess();
125 
126             Console.WriteLine($"Breakfast is ready!{Environment.NewLine}");
127             st.Stop();
128             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 结束，耗时 = {st.ElapsedMilliseconds.ToString("###,###")} 毫秒");
129         }
130 
131         [Benchmark]
132         public async Task RunV5()
133         {
134             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 开始....");
135             var st = Stopwatch.StartNew();
136 
137             Coffee cup = PourCoffee();
138             PourCoffeeSuccess();
139 
140             var eggsTask = FryEggsAsync(2);
141             var baconTask = FryBaconAsync(3);
142             var toastTask = MakeToastWithButterAndJamAsync(2);
143 
144             await eggsTask;
145             FryEggsSuccess();
146 
147             await baconTask;
148             FryBaconSuccess();
149 
150             var toast = await toastTask;
151             ToastBreadSuccess();
152 
153             Juice oj = PourOJ();
154             PourOJSuccess();
155 
156             Console.WriteLine($"Breakfast is ready!{Environment.NewLine}");
157             st.Stop();
158             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 结束，耗时 = {st.ElapsedMilliseconds.ToString("###,###")} 毫秒");
159         }
160 
161         [Benchmark]
162         public async Task RunV6()
163         {
164             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 开始....");
165             var st = Stopwatch.StartNew();
166 
167             Coffee cup = PourCoffee();
168             PourCoffeeSuccess();
169 
170             var eggsTask = FryEggsAsync(2);
171             var baconTask = FryBaconAsync(3);
172             var toastTask = MakeToastWithButterAndJamAsync(2);
173 
174             await Task.WhenAll(eggsTask, baconTask, toastTask);
175             FryEggsSuccess();
176             FryBaconSuccess();
177             ToastBreadSuccess();
178 
179             Juice oj = PourOJ();
180             PourOJSuccess();
181 
182             Console.WriteLine($"Breakfast is ready!{Environment.NewLine}");
183             st.Stop();
184             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 结束，耗时 = {st.ElapsedMilliseconds.ToString("###,###")} 毫秒");
185         }
186 
187         [Benchmark]
188         public async Task RunV7()
189         {
190             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 开始....");
191             var st = Stopwatch.StartNew();
192 
193             Coffee cup = PourCoffee();
194             PourCoffeeSuccess();
195 
196             var eggsTask = FryEggsAsync(2);
197             var baconTask = FryBaconAsync(3);
198             var toastTask = MakeToastWithButterAndJamAsync(2);
199             var breakfastTasks = new List<Task>() { eggsTask, baconTask, toastTask };
200             while (breakfastTasks.Count > 0)
201             {
202                 var task = await Task.WhenAny(breakfastTasks);
203                 if (task == eggsTask)
204                 {
205                     FryEggsSuccess();
206                 }
207                 else if (task == baconTask)
208                 {
209                     FryBaconSuccess();
210                 }
211                 else if (task == toastTask)
212                 {
213                     ToastBreadSuccess();
214                 }
215 
216                 breakfastTasks.Remove(task);
217             }
218 
219             Juice oj = PourOJ();
220             PourOJSuccess();
221 
222             Console.WriteLine($"Breakfast is ready!{Environment.NewLine}");
223             st.Stop();
224             Console.WriteLine($"{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff")} 结束，耗时 = {st.ElapsedMilliseconds.ToString("###,###")} 毫秒");
225         }
226 
227 
228         /// <summary>
229         /// 倒一杯橙汁
230         /// </summary>
231         /// <returns></returns>
232         private static Juice PourOJ()
233         {
234             Console.WriteLine("Pouring orange juice(倒一杯橙汁)");
235             Thread.Sleep(100);
236             return new Juice();
237         }
238         /// <summary>
239         /// 面包加果酱
240         /// </summary>
241         /// <param name="toast"></param>
242         private static void ApplyJam(Toast toast)
243         {
244             Thread.Sleep(50);
245             Console.WriteLine("Putting jam on the toast(面包加果酱)");
246         }
247         /// <summary>
248         /// 面包加黄油
249         /// </summary>
250         /// <param name="toast"></param>
251         private static void ApplyButter(Toast toast)
252         {
253             Thread.Sleep(50);
254             Console.WriteLine("Putting butter on the toast(面包加黄油)");
255         }
256         /// <summary>
257         /// 烤面包
258         /// </summary>
259         /// <param name="slices"></param>
260         /// <returns></returns>
261         private static Toast ToastBread(int slices)
262         {
263             Console.WriteLine("Start toasting(烤面包)...");
264             for (int slice = 0; slice < slices; slice++)
265             {
266                 Console.WriteLine("Putting a slice of bread in the toaster");
267                 Thread.Sleep(100);
268             }
269             Console.WriteLine("Remove toast from toaster");
270 
271             return new Toast();
272         }
273         /// <summary>
274         /// 煎培根
275         /// </summary>
276         /// <param name="slices"></param>
277         /// <returns></returns>
278         private static Bacon FryBacon(int slices)
279         {
280             Console.WriteLine($"putting {slices} slices of bacon in the pan(煎培根)");
281             Console.WriteLine("cooking first side of bacon...");
282             for (int slice = 0; slice < slices; slice++)
283             {
284                 Console.WriteLine("flipping a slice of bacon");
285                 Thread.Sleep(100);
286             }
287             Console.WriteLine("cooking the second side of bacon...");
288             Console.WriteLine("Put bacon on plate");
289 
290             return new Bacon();
291         }
292         /// <summary>
293         /// 煎鸡蛋
294         /// </summary>
295         /// <param name="howMany"></param>
296         /// <returns></returns>
297         private static Egg FryEggs(int howMany)
298         {
299             Console.WriteLine("Warming the egg pan(煎鸡蛋)...");
300             Console.WriteLine($"cracking {howMany} eggs");
301             Console.WriteLine("cooking the eggs ...");
302             for (int i = 0; i < howMany; i++)
303             {
304                 Thread.Sleep(100);
305             }
306             Console.WriteLine("Put eggs on plate");
307 
308             return new Egg();
309         }
310         /// <summary>
311         /// 倒咖啡
312         /// </summary>
313         /// <returns></returns>
314         private static Coffee PourCoffee()
315         {
316             Console.WriteLine("Pouring coffee(倒咖啡)");
317             Thread.Sleep(100);
318             return new Coffee();
319         }
320 
321         private static void PourOJSuccess()
322         {
323             Console.WriteLine("oj is ready(橙汁已倒好)");
324         }
325         private static void ToastBreadSuccess()
326         {
327             Console.WriteLine($"toast is ready(面包已烤好){Environment.NewLine}");
328         }
329         private static void FryBaconSuccess()
330         {
331             Console.WriteLine($"bacon is ready({3}片培根已煎好){Environment.NewLine}");
332         }
333         private static void FryEggsSuccess()
334         {
335             Console.WriteLine($"eggs are ready({2}个鸡蛋已煎好){Environment.NewLine}");
336         }
337         private static void PourCoffeeSuccess()
338         {
339             Console.WriteLine($"coffee is ready(咖啡已倒好){Environment.NewLine}");
340         }
341 
342 
343         /// <summary>
344         /// 煎鸡蛋
345         /// </summary>
346         /// <param name="howMany"></param>
347         /// <returns></returns>
348         private static async Task<Egg> FryEggsAsync(int howMany)
349         {
350             Console.WriteLine("Warming the egg pan(煎鸡蛋)...");
351             Console.WriteLine($"cracking {howMany} eggs");
352             Console.WriteLine("cooking the eggs ...");
353             for (int i = 0; i < howMany; i++)
354             {
355                 await Task.Delay(100);
356             }
357             Console.WriteLine("Put eggs on plate");
358 
359             return new Egg();
360         }
361         /// <summary>
362         /// 煎培根
363         /// </summary>
364         /// <param name="slices"></param>
365         /// <returns></returns>
366         private static async Task<Bacon> FryBaconAsync(int slices)
367         {
368             Console.WriteLine($"putting {slices} slices of bacon in the pan(煎培根)");
369             Console.WriteLine("cooking first side of bacon...");
370             for (int slice = 0; slice < slices; slice++)
371             {
372                 Console.WriteLine("flipping a slice of bacon");
373                 await Task.Delay(100);
374             }
375             Console.WriteLine("cooking the second side of bacon...");
376             Console.WriteLine("Put bacon on plate");
377 
378             return new Bacon();
379         }
380         /// <summary>
381         /// 烤面包
382         /// </summary>
383         /// <param name="slices"></param>
384         /// <returns></returns>
385         private static async Task<Toast> ToastBreadAsync(int slices)
386         {
387             Console.WriteLine("Start toasting(烤面包)...");
388             for (int slice = 0; slice < slices; slice++)
389             {
390                 Console.WriteLine("Putting a slice of bread in the toaster");
391                 await Task.Delay(100);
392             }
393             //Console.WriteLine("Fire! Toast is ruined!");
394             //throw new InvalidOperationException("The toaster is on fire");
395             Console.WriteLine("Remove toast from toaster");
396 
397             return new Toast();
398         }
399         /// <summary>
400         /// 烤面包 + 黄油 + 果酱
401         /// </summary>
402         /// <param name="number"></param>
403         /// <returns></returns>
404         private static async Task<Toast> MakeToastWithButterAndJamAsync(int number)
405         {
406             var toast = await ToastBreadAsync(number);
407             ApplyButter(toast);
408             ApplyJam(toast);
409 
410             return toast;
411         }
412     }
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五、工作机制与原理

六、总结

  • 推荐做法

  1. 在.NET中，推荐使用基于任务的异步模式。它基于 System.Threading.Tasks 命名空间中的 Task 和 Task<TResult> 类型，这些类型用于表示异步操作。

  2. 避免 Async Void 最好使用 async Task 方法而不是 async void 方法。

  3. 始终使用 Async 不要混合阻塞式代码和异步代码。

  4. 配置上下文尽可能使用 ConfigureAwait(false)。

Async/Await 异步编程中的最佳做法 | Microsoft Docs

  • 使用过程中可能出现的误区

  1. Task.Factory.StartNew(async () =>{});的写法

如下面的错误写法： 

  var task= Task.Factory.StartNew(async () =>
  {
      // task job.
      await Task.Delay(1000);
  });
  await task;

正确写法

方式一（推荐）：

  var task= Task.Run(async () =>
  {
      // task job.
      await Task.Delay(1000);
  });
  await task;

方式二：

  var task= Task.Factory.StartNew(async () =>
  {
      // task job.
      await Task.Delay(1000);
  }).Unwrap();
  await task;

方式三：

  var task= await Task.Factory.StartNew(async () =>
  {
      // task job.
      await Task.Delay(1000);
  });
  await task;

 相关文章：Task.Run(), Task.Factory.StartNew() 和 New Task() 的行为不一致分析 

七、特别声明

  • 本文引用了其他博友写的文章，如果有涉及到侵权问题请及时联系我进行删除。

  • 本文涉及到的一些文章未经过严格的推敲于论证，如果大家有发现问题欢迎大家指出，然后我再进行更改。

  • 涉及到这个模块好的文章也欢迎大家进行推荐或自荐，本人阅读论证后会进行引用添加。

posted @ 2022-07-02 15:32  lanwah  阅读(781)  评论(0)  编辑  收藏  举报