How can the number of concurrently running threads in a program be controlled?

In C#, the Semaphore or SemaphoreSlim class is often used to control the number of concurrently running threads. They allow limiting the number of threads that can execute a certain section of code simultaneously.

Example of using SemaphoreSlim:

using System;
using System.Threading;

class Program
{
    static SemaphoreSlim semaphore = new SemaphoreSlim(3); // maximum 3 threads at the same time

    static void Worker(int id)
    {
        semaphore.Wait(); // request permission
        Console.WriteLine($"Thread {id} started working");
        Thread.Sleep(1000); // simulate work
        Console.WriteLine($"Thread {id} finished working");
        semaphore.Release(); // release permission
    }

    static void Main()
    {
        for (int i = 1; i <= 10; i++)
        {
            int localId = i;
            new Thread(() => Worker(localId)).Start();
        }
    }
}

In this example, no more than three threads can work simultaneously.