使用Nito.AsyncEx实现异步锁（转）

转载地址：http://www.cnblogs.com/1zhk/p/5269279.html

Lock是常用的同步锁，但是我们无法在Lock的内部实现异步调用，比如我们无法使用await.

以下面的代码为例，当你在lock内部使用await时，VS会报错提醒。

最简单的解决办法就是使用第三方的库Nito.AsyncEx。可以通过Nuget安装。

通过AsyncLock就可以在锁的内部实现异步操作了。

样例代码如下：

 1 public class AsyncLockDemo
 2     {
 3         //private readonly object _mutex = new object();
 4         private readonly AsyncLock _mutex = new AsyncLock();
 5         private int i = 0;
 6         public void Execute()
 7         {
 8             Console.WriteLine("before call foo1: "+ i);
 9
10             Foo1().ContinueWith(new Action<Task>(t =>
11             {
12                 Console.WriteLine("foo1 completed: " + i);
13             }));
14
15             Console.WriteLine("after call foo1: " + i);
16
17             Console.WriteLine("before call foo2: " + i);
18
19             Foo2().ContinueWith(new Action<Task>(t =>
20             {
21                 Console.WriteLine("foo2 completed: " + i);
22             }));
23
24             Console.WriteLine("after call foo2: " + i);
25         }
26
27         public async Task Foo1()
28         {
29             using (await _mutex.LockAsync())
30             {
31                 await Task.Delay(TimeSpan.FromSeconds(1));
32                 Console.WriteLine("Foo1 start: " + i);
33                 await DoSomethingAsync(1);
34                 Console.WriteLine("Foo1 end: " + i);
35             }
36         }
37
38         public async Task Foo2()
39         {
40             using (await _mutex.LockAsync())
41             {
42                 Console.WriteLine("Foo2 start: " + i);
43                 //await Task.Delay(TimeSpan.FromSeconds(1));
44                 await DoSomethingAsync(2);
45                 Console.WriteLine("Foo2 end: " + i);
46             }
47         }
48
49         private Task DoSomethingAsync(int j)
50         {
51             return Task<string>.Run(() =>
52             {
53                 Thread.Sleep(2000);
54                 i = j;
55             });
56         }
57     }

运行结果如下：