C#开启线程的几种方式

方式一：通过委托发起线程（BeginInvoke）：

Func<int, int> a = Test;
IAsyncResult ar = a.BeginInvoke(20, OnCallBack, a);//倒数第二个参数是一个委托类型的参数，表示回调函数，当线程结束时会调用这个委托指向的方法；倒数第一个参数用来给回调函数传递数据；通过ar获取数据a

方式二：通过Thread发起线程，thread创建的线程都是前台线程，线程池创建的线程都是后台线程

1. thread参数为静态方法

        static void Downloadfile()
        {
            Console.WriteLine("开始下载" + Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep(2000);
            Console.WriteLine("下载完成");
        }

        static void Main(string[] args)
        {
            Thread t = new Thread(Downloadfile);
            t.Start();
            Console.WriteLine("main");
            Console.ReadKey();
        }

2. lamda表达式

Thread t = new Thread(() =>
    {
        Console.WriteLine("开始下载" + Thread.CurrentThread.ManagedThreadId);
        Thread.Sleep(2000);
        Console.WriteLine("下载完成");
    });
t.Start();    

3. Thread参数为普通方法

    class Program
    {
        static void Downloadfile(object filename)
        {
            Console.WriteLine("开始下载" + filename+ Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep(2000);
            Console.WriteLine("下载完成"+filename);
        }

        static void Main(string[] args)
        {
            //Thread t = new Thread(() =>
            //{

            //    Console.WriteLine("开始下载" + Thread.CurrentThread.ManagedThreadId);
            //    Thread.Sleep(2000);
            //    Console.WriteLine("下载完成");
            //});
            //Thread t = new Thread(Downloadfile);
            MyThread my = new MyThread("xxx.bt", "http://www.xxx.bbs");
            Thread t = new Thread(my.DownFile);
            t.Start();
            Console.WriteLine("main");
            Console.ReadKey();
        }
    }

    class MyThread
    {
        private string filename;
        private string filepath;
        public MyThread(string fileName, string filePath)
        {
            this.filename = fileName;
            this.filepath = filePath;
        }

        public void DownFile()
        {
            Console.WriteLine("开始下载" + filepath + filename);
            Thread.Sleep(2000);
            Console.WriteLine("下载完成");
        }

    }
}

方式三：线程池：适合用于小任务线程,

WaitCallback:将方法排入队列以便执行，WaitCallback，表示要执行的方法。如果将方法成功排入队列，则为 true；否则为 false。

    class Program
    {
        static void ThreadMethod(object state)
        {
            Console.WriteLine("线程开始"+Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep(2000);
            Console.WriteLine("线程结束");
        }
        static void Main(string[] args)
        {
            ThreadPool.QueueUserWorkItem(ThreadMethod);
            ThreadPool.QueueUserWorkItem(ThreadMethod);
            ThreadPool.QueueUserWorkItem(ThreadMethod);
            ThreadPool.QueueUserWorkItem(ThreadMethod);
            ThreadPool.QueueUserWorkItem(ThreadMethod);
            Console.ReadKey();
        }
    }

方式四：任务线程

1. 通过Task创建

class Program
    {
        static void ThreadMethod()
        {
            Console.WriteLine("任务开始" + Thread.CurrentThread.ManagedThreadId);
            Thread.Sleep(2000);
            Console.WriteLine("任务结束");
        }

        static void Main(string[] args)
        {
            Task t = new Task(ThreadMethod);
            t.Start();
            Console.WriteLine("main");
            Console.ReadKey();
        }
    }

2. 通过TaskFactory创建

TaskFactory tf = new TaskFactory();
tf.StartNew(ThreadMethod);   

　tf.StartNew(ThreadMethod);
　tf.StartNew(ThreadMethod)；