.net core 信号量 SemaphoreSlim

[ren8179]

System.Threading.Semaphore 是Win32信号量对象(计数信号量)的包装, 是系统范围的信号量,因此可以在多个进程之间使用.

System.Threading.SemaphoreSlim 是CLR提供的一种轻量级的快速信号量，用于在预期等待时间很短的情况下在单个进程内等待。 SemaphoreSlim 类是用于在单个应用内进行同步的建议信号量。

如果需要有跨进程或AppDomain的同步时，可以考虑使用Semaphore。Semaphore是取得的Windows 内核的信号量，所以在整个系统中是有效的。它主要的接口是Release和WaitOne，使用的方式和SemaphoreSlim是一致的。

用信号量SemaphoreSlim代替锁

//Instantiate a Singleton of the Semaphore with a value of 1. This means that only 1 thread can be granted access at a time.
static SemaphoreSlim semaphoreSlim = new SemaphoreSlim(1,1);

//Asynchronously wait to enter the Semaphore. If no-one has been granted access to the Semaphore, code execution will proceed, otherwise this thread waits here until the semaphore is released 
await semaphoreSlim.WaitAsync();
try
{
    await Task.Delay(1000);
}
finally
{
    //When the task is ready, release the semaphore. It is vital to ALWAYS release the semaphore when we are ready, or else we will end up with a Semaphore that is forever locked.
    //This is why it is important to do the Release within a try...finally clause; program execution may crash or take a different path, this way you are guaranteed execution
    semaphoreSlim.Release();
}