C#多线程中如何等待所有线程的任务都执行完成呢？在.net 4.0以4.0+中，有Task.WaitAll(params Task[] tasks)方法来等待所有Task[],而不需要更多的操作。按照微软官方的文档，我写了一个实例来调试和说明：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks; namespace ConsoleApp { class Program { static void Main(string[] args) { var bookShop = new BookShop(); bookShop.Run(); } } pulic class Book { public int Id { get; set; } public string Name { get; set; } } public class BookShop { Random rand = new Random(); Queue<Book> queueBook = new Queue<Book>(); int Max = 10000; int EachCount = 500; int Cur = 0; void LoadData() { if (Cur >= Max) { //when Cur>=Max,return Console.WriteLine("Reached max value!"); return; } Console.WriteLine("Loading data..."); for (int i = Cur; i < EachCount + Cur; i++) { Thread.Sleep(10); Console.Write(i + " "); //insert data into Queue<Book> queueBook.Enqueue(new Book { Id = i, Name = "Name_" + i }); } Console.WriteLine(""); Cur += EachCount; Console.WriteLine("Data loaded successful,{0}...", queueBook.Count); } public void Run() { LoadData(); Console.WriteLine("Tasks have started..."); do { Task[] tasks = new Task[10]; for (int i = 0; i < 10; i++) { tasks[i] = Task.Factory.StartNew(() => DoSomeWork(1000 * 1)); } //// Wait for all tasks to complete. Task.WaitAll(tasks); //when Queue<Book> is empty,reload data... LoadData(); } while (queueBook.Count > 0); //when Cur>=Max,break the while loop Console.WriteLine("All tasks have completed."); Console.ReadKey(); } void DoSomeWork(int val) { while (queueBook.Count > 0) { var m = queueBook.Dequeue(); Console.WriteLine("DoSomeWork start,i={0},Current thread id:{1}...", m.Id, Thread.CurrentThread.ManagedThreadId); var sleep = rand.Next(10, 200); // Pretend to do something. Thread.Sleep(sleep); Console.WriteLine("DoSomeWork has completed,sleep:{0},i={1}", sleep, m.Id); } } } }