Asp.Net Core 实现异步操作锁

 

/设置同时访问线程最大数量
static SemaphoreSlim _semaphore = new SemaphoreSlim(4);

static void AccessDatabase(string name, int seconds)
{
   Console.WriteLine($"{name} waits to access a database");
   _semaphore.Wait();
   Console.WriteLine($"{name} was granted an access to a database");
   Thread.Sleep(TimeSpan.FromSeconds(seconds));
   Console.WriteLine($"{name} is completed");
   _semaphore.Release();
}

static void Main(string[] args)
{
   for (int i = 1; i < 6; i++)
   {
       string threadName = $"Thread{i}";
       int secondsToWait = 2 + 2 * i;
       var t = new Thread(() => AccessDatabase(threadName, secondsToWait));
       t.Start();
   }
}

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上面的代码 new 了一个 SemaphoreSlim 对象，设置访问线程最大数量为 4，开启 5 个线程，发现，
线程 5 一开始一直处于等待状态，直到线程 1 完成了，调用了 _semaphore.Release() 释放，线程 5 才能执行后面的代码