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Semaphore in C#
The semaphore class lets you set a limit on the number of threads that have access to a critical section. The class is used to control access to a pool of resources. System.Threading.Semaphore is the namespace for Semaphore because it has all the methods and properties required to implement Semaphore.
For using a semaphore in C#, you just need to instantiate an instance of a Semaphore object. It has minimum of two arguments −
Reference
−
MSDN
| Sr.No. | Constructor & Description |
|---|---|
| 1 | Semaphore(Int32,Int32) Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries. |
| 2 | Semaphore(Int32,Int32,String) − Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, and optionally specifying the name of a system semaphore object. |
| 3 | Semaphore(Int32,Int32,String,Boolean) Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, optionally specifying the name of a system semaphore object, and specifying a variable that receives a value indicating whether a new system semaphore was created. |
Let us now see an example:
Here, we have used the following Semaphore constructor that initializes a new instance of the Semaphore class, specifying the maximum number of concurrent entries and optionally reserving some entries.
static Semaphore semaphore = new Semaphore(2, 2);
Example
using System;
using System.Threading;
namespace Program
{
class Demo
{
static Thread[] t = new Thread[5];
static Semaphore semaphore = new Semaphore(2, 2);
static void DoSomething()
{
Console.WriteLine("{0} = waiting", Thread.CurrentThread.Name);
semaphore.WaitOne();
Console.WriteLine("{0} begins!", Thread.CurrentThread.Name);
Thread.Sleep(1000);
Console.WriteLine("{0} releasing...", Thread.CurrentThread.Name);
semaphore.Release();
}
static void Main(string[] args)
{
for (int j = 0; j < 5; j++)
{
t[j] = new Thread(DoSomething);
t[j].Name = "thread number " + j;
t[j].Start();
}
Console.Read();
}
}
}Output
The following is the output
thread number 2 = waiting thread number 0 = waiting thread number 3 = waiting thread number 1 = waiting thread number 4 = waiting thread number 2 begins! thread number 1 begins! thread number 2 releasing... thread number 1 releasing... thread number 4 begins! thread number 3 begins! thread number 4 releasing... thread number 0 begins! thread number 3 releasing... thread number 0 releasing...
Updated on: 01-Apr-2020
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