C# 多线程使用信号量控制处理效率，统计活动中的线程

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
 
namespace ConsoleApp1
{
    class Program
    {
        //信号量Semaphore限制可同时访问某一资源或资源池的线程数。指示控制的资源初始和最大线程并发数为2
        static Semaphore sema = new Semaphore(1, 1);
        static int aliveCount = 0;
        static object obj = new object();
 
        static void Main(string[] args)
        {
            for (int i = 0; i < 10; i++)
            {
                var thread = new Thread(Test) { Name = $"Thread{i}" };
                thread.Start();
            }
            var timer = new System.Timers.Timer();
            timer.Interval = 1000;
            timer.Elapsed += MTMShareCountry;
            timer.Enabled = true;
            timer.AutoReset = true;
            timer.Start();
            Console.ReadKey();
        }
 
        private static void MTMShareCountry(object sender, System.Timers.ElapsedEventArgs e)
        {
            Console.WriteLine($"现在alive线程数: {aliveCount}");
        }
 
 
        static void Test()
        {
            lock (obj)
            {
                aliveCount++;
            }
            string threadName = Thread.CurrentThread.Name;
            Console.WriteLine($"{threadName} 正在等待一个许可证.......");
            //申请一个许可证
            sema.WaitOne();
 
            Console.WriteLine($"............... {threadName} 申请到许可证................");
            for (int k = 0; k < 3; k++)
            {
                Console.WriteLine($"ThreadName:{threadName} 循环:{k}");
                Thread.Sleep(1000);
            }
            sema.Release();   //释放一个许可证
            lock (obj)
            {
                aliveCount--;
            }
        }
    }
}