1.什么是线程？

进程作为操作系统执行程序的基本单位，拥有应用程序的资源，进程包含线程，进程的资源被线程共享，线程不拥有资源。

 

2.前台线程和后台线程的区别？

程序关闭时，后台线程直接关闭，但前台线程会执行完后关闭。

通过Thread类新建线程默认为前台线程。其他方式创建的都是后台线程。

 

多线程的几种方式

一. 异步多线程

static void Main(string[] args)
        {
            Console.WriteLine("----------主程序开始，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);
            for(int i = 0; i< 5;i++)
            {
                Action<string> action = t =>
                {
                    for(int k = 0; k< 1000000000;k++)
                    { }
                    Console.WriteLine("当前参数是{0},当前线程是{1}",t,Thread.CurrentThread.ManagedThreadId);
                };

                action.BeginInvoke("参数是" + i, null, null);
            }
            Console.WriteLine("----------主程序结束，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);
            Console.Read();
        }
    }

二. Threads线程

static void Main(string[] args)
        {
            Console.WriteLine("----------主程序开始，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);
            for(int i = 0; i< 5;i++)
            {
                ParameterizedThreadStart threadStart = t =>
                {
                    for (int k = 0; k < 1000000000; k++)
                    { }
                    Console.WriteLine("当前参数是{0},当前线程是{1}", t, Thread.CurrentThread.ManagedThreadId);
                };

                Thread thread = new Thread(threadStart);

                thread.Start(i);
            }
            Console.WriteLine("----------主程序结束，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);

            Console.Read();
        }

三. ThreadPool线程池\

static void Main(string[] args)
        {
            Console.WriteLine("----------主程序开始，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);
            for(int i = 0; i< 5;i++)
            {
                WaitCallback waitCallback = t =>
                {
                    for (int k = 0; k < 1000000000; k++)
                    { }
                    Console.WriteLine("当前参数是{0},当前线程是{1}", t, Thread.CurrentThread.ManagedThreadId);
                };

                ThreadPool.QueueUserWorkItem(waitCallback, i);
            }
            Console.WriteLine("----------主程序结束，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);

            Console.Read();
        }

四. Task

static void Main(string[] args)
        {
            Console.WriteLine("----------主程序开始，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);

            TaskFactory taskFactory = new TaskFactory();

            for (int i = 0; i< 5;i++)
            {
                Action<object> action = t =>
                {
                    for (int k = 0; k < 1000000000; k++)
                    { }
                    Console.WriteLine("当前参数是{0},当前线程是{1}", t, Thread.CurrentThread.ManagedThreadId);
                };

                taskFactory.StartNew(action,i);
            }
            Console.WriteLine("----------主程序结束，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);

            Console.Read();
        }

五. Parallel

static void Main(string[] args)
        {
            Console.WriteLine("----------主程序开始，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);


            Action action1 = () =>
            {
                for (int k = 0; k < 1000000000; k++)
                { }
                Console.WriteLine("当前参数是1,当前线程是{0}", Thread.CurrentThread.ManagedThreadId);
            };
            Action action2 = () =>
            {
                for (int k = 0; k < 1000000000; k++)
                { }
                Console.WriteLine("当前参数是2,当前线程是{0}", Thread.CurrentThread.ManagedThreadId);
            };
            Action action3 = () =>
            {
                for (int k = 0; k < 1000000000; k++)
                { }
                Console.WriteLine("当前参数是3,当前线程是{0}", Thread.CurrentThread.ManagedThreadId);
            };

            Parallel.Invoke(action1, action2, action3);

            Console.WriteLine("----------主程序结束，线程ID是{0}-----------------", Thread.CurrentThread.ManagedThreadId);

            Console.Read();
        }

上面简单介绍了5种多线程的使用方式