c# 多线程概览

场景：1~1000累加求和

只考虑如何启用多线程计算，不考虑线程同步

实现方式：

1.Thread thread=new Thread(new ThreadStart(some delegate)); 无参数启动新线程。

2.Thread thread=new Thread(new ParameterizedThreadStart(some delegate,params)); 带参数启动新线程。

3.将线程操作封装为一个独立方法，其中使用匿名方法的方式将外部参数导入。

4.ThreadPool.QueueUserWorkItem(delegeate,params)带参数的线程池方法，

    注意线程池中分配的线程都是background线程，主线程终止会导致子线程终止。

5.Task，都多重方式，底层使用的Threadpool，需要使用wait方法阻塞主线程。

6.构造一个包含参数、操作的类，通过类的属性将参数传递给操作。

7.通过委托的方式，可以传参，并且可以有返回值。

以上除了委托方式，其他可以传参的方式，都可以通过把返回值封装在参入参数中，使用引用的方式获得返回值。

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace multithreadTest
{
    class Program
    {
        static Stopwatch watch = new Stopwatch();
        static int length = 100;
        static int count;
        static void Main(string[] args)
        {
            
            Console.WriteLine("Main Thread:{0}", Thread.CurrentThread.ManagedThreadId);
            //CaculateSum();
            //NoInputAndReturn();
            //MultiInputNoReturn_Anonymous();
            //MultiInputNoReturn_ParameterizedThread();
            //MultiInputNoReturn_ThreadPool();
            MultiInputNoReturn_Task();
            //MultiInputNoReturn_UseClassProperty();
            //MultiInputWithReturn_Delegate();
            Console.WriteLine("Main Thread Exit:{0}", Thread.CurrentThread.Name);
        }

        #region 没有输入，没有返回
        /// <summary>
        /// 没有输入，没有返回
        /// </summary>
        public static void NoInputAndReturn()
        {
            ThreadStart ts = new ThreadStart(CaculateSum);
            Thread thread=new Thread(ts);
            thread.Start();
        }

        /// <summary>
        /// 1~1000求和 无输入 无返回
        /// </summary>
        public static void CaculateSum()
        {
            watch.Reset();
            watch.Start();
            Console.WriteLine("IsBackground:{0}", Thread.CurrentThread.IsBackground);
            Console.WriteLine("Thread Start:{0}", Thread.CurrentThread.ManagedThreadId);
            int count = 0;
            for (var i = 0; i <= 1000; i++)
            {
                count += i;
                Thread.Sleep(5);
            }
            watch.Stop();
            Console.WriteLine("Thread Exit:{0},Count:{1},Time:{2}", Thread.CurrentThread.ManagedThreadId, count, watch.Elapsed);
        }
        #endregion


        #region 多输入 无返回
        #region 匿名方法
        /// <summary>
        /// 多输入 无返回 匿名方法
        /// </summary>
        public static void MultiInputNoReturn_Anonymous()
        {
            for(var i=0;i<1000;i+=(length+1))
            {
                CaculateSum_Anonymous(i, i + length > 1000 ? 1000 : i + length);
            }
        }


        /// <summary>
        /// start~end求和 匿名方法方式
        /// </summary>
        /// <returns></returns>
        public static void CaculateSum_Anonymous(int start, int end)
        {
            Thread t = new Thread(new ThreadStart(delegate() {
                watch.Reset();
                watch.Start();
                int count = 0;
                for (var i = start; i <= end; i++)
                {
                    count += i;
                    Thread.Sleep(5);
                }
                watch.Stop();
                Console.WriteLine("Thread Exit:{0},Count:{1},Time:{2}", Thread.CurrentThread.ManagedThreadId, count, watch.Elapsed);
            }));
            t.Start();
        }
        #endregion

        class StartEnd
        {
            public int start;
            public int end;
        }

        #region ParameterizedThread包装参数
       
        public static void MultiInputNoReturn_ParameterizedThread()
        {
            for (var i = 0; i < 1000; i += (length+1))
            {
                ParameterizedThreadStart ts = new ParameterizedThreadStart(CaculateSum_ParameterizedThread);
                Thread thread = new Thread(ts);
                thread.Start(new StartEnd() { start = i, end = i + length > 1000 ? 1000 : i + length });
            }
        }

        /// <summary>
        /// 0~end求和 一个参数 无返回
        /// </summary>
        /// <returns></returns>
        public static void CaculateSum_ParameterizedThread(object se)
        {
            watch.Reset();
            watch.Start();
            var start=((StartEnd)se).start;
            var end=((StartEnd)se).end;
            int count = 0;
            for (var i =start ; i <= end; i++)
            {
                count += i;
                Thread.Sleep(5);
            }
            watch.Stop();
            Console.WriteLine("Thread Exit:{0},Count:{1},Time:{2}", Thread.CurrentThread.ManagedThreadId, count, watch.Elapsed);
        }
        #endregion

        #region ThreadPool 包装参数
        public static void MultiInputNoReturn_ThreadPool()
        {
            for (var i = 0; i < 1000; i += (length + 1))
            {
                ThreadPool.QueueUserWorkItem(CaculateSum_ParameterizedThread, 
                    new StartEnd() { start = i, end = i + length > 1000 ? 1000 : i + length });
            }
            
            //threadpool中的线程都是background的，如果主线程提前终止，会终止子线程的操作
            Console.WriteLine("Main thread does some work, then sleeps.");
            Thread.Sleep(5000);

            Console.WriteLine("Main thread exits.");
        }
        #endregion

        #region Task 包装参数
        public static void MultiInputNoReturn_Task()
        {
            for (var i = 0; i < 1000; i += (length + 1))
            {
                Task t = new Task(CaculateSum_ParameterizedThread, new StartEnd() { start = i, end = i + length > 1000 ? 1000 : i + length });
                t.Start();
                //Task是基于线程池的,如果不使用wait会被主线程终止
                t.Wait();
            }
            Console.WriteLine("Main thread does some work, then sleeps.");

            Console.WriteLine("Main thread exits.");
        }
        #endregion

        #region 通过类属性
        /// <summary>
        /// 多输入 无返回 通过类属性
        /// </summary>
        public static void MultiInputNoReturn_UseClassProperty()
        {
            for (var i = 0; i < 1000; i += (length+1))
            {
                var sum = new SumTest();
                ThreadStart start = new ThreadStart(sum.GetSum);
                sum.Start = i;
                sum.End = i + length > 1000 ? 1000 : i + length;
                Thread t = new Thread(start);
                t.Start();
            }
        }

        public class SumTest
        {
            public int Start;
            public int End;

            public void GetSum()
            {
                watch.Reset();
                watch.Start();
                int count = 0;
                for (var i = this.Start; i <= this.End; i++)
                {
                    count += i;
                    Thread.Sleep(5);
                }
                watch.Stop();
                Console.WriteLine("Thread Exit:{0},Count:{1},Time:{2}", Thread.CurrentThread.ManagedThreadId, count, watch.Elapsed);
            }
        }

        #endregion
        #endregion

        #region 传参 有返回 委托

        delegate TimeSpan GetSumMethod(int start, int end);
        static GetSumMethod getSum;
        public static void MultiInputWithReturn_Delegate()
        {
            int count=0;
            TimeSpan ts = new TimeSpan();
            for (var i = 0; i < 1000; i += (length+1))
            {
                GetSumMethod getSumMethod = CaculateSum;
                getSumMethod.BeginInvoke(i, i + length > 1000 ? 1000 : i + length,
                    new AsyncCallback(delegate(IAsyncResult result) { ts += getSumMethod.EndInvoke(result); }), null);
            }
            
            Thread.Sleep(6000);
            Console.WriteLine("TimeSpan:{0}", ts);
            Console.ReadKey();
        }

        public static TimeSpan CaculateSum(int start, int end)
        {
            watch.Reset();
            watch.Start();
            Console.WriteLine("Thread Start:{0}", Thread.CurrentThread.ManagedThreadId);
            int count = 0;
            for (var i = start; i <= end; i++)
            {
                count += i;
                Thread.Sleep(5);
            }
            watch.Stop();
            Console.WriteLine("Thread Exit:{0},Count:{1},Time:{2}", Thread.CurrentThread.ManagedThreadId, count, watch.Elapsed);
            return watch.Elapsed;
        }

        #endregion

       
    }
}