使用 Thread 的请参考另一个贴子：https://www.cnblogs.com/pencilstart/p/15865400.html

注意，由于 .NET 3.5下并没有官方实现的 Task 库，所以，是通过 VS 中 NuGet 取得的 非官方 实现的 Task 库，调用接口与官方.NET 4.0 后的应该是差不多的。

 1 using System;
 2 using System.Threading;
 3 using System.Threading.Tasks;
 4 
 5 namespace testTask
 6 {
 7     class Program
 8     {
 9         Semaphore se = new Semaphore(1, 1);
10 
11         void test()
12         {
13             object param1 = new object[] { "Thread A", 1000 };
14             object param2 = new object[] { "Thread B", 20 };
15 
16             Action<object> a1 = (x) => TaskProc(x);
17 
18             Task task1 = new TaskFactory().StartNew(a1, param1);
19             Task task2 = new TaskFactory().StartNew(a1, param2);
20 
21             Task.WaitAll(task1, task2);
22         }
23 
24         static void Main(string[] args)
25         {
26             Program p = new Program();
27 
28             p.test();
29 
30             Console.WriteLine("main end, mainthreadid = {0}", System.Threading.Thread.CurrentThread.ManagedThreadId);
31         }
32 
33         void TaskProc(object args)
34         {
35             string name = (string)((object[])args)[0];
36             int startdelay = (int)((object[])args)[1];
37 
38             Console.WriteLine("{0}: COME IN, threadid = {1}", name, System.Threading.Thread.CurrentThread.ManagedThreadId);
39 
40             System.Threading.Thread.Sleep(startdelay);
41 
42             Console.WriteLine("{0}: START, threadid = {1}", name, System.Threading.Thread.CurrentThread.ManagedThreadId);
43 
44             for (int i = 0; i < 10; ++i)
45             {
46                 se.WaitOne();
47 
48                 Random r = new Random();
49 
50                 int s = r.Next(50, 1000);
51 
52                 Console.WriteLine("{0}: i = {1}, sleep({2}), threadid = {3}", name, i, s, System.Threading.Thread.CurrentThread.ManagedThreadId);
53 
54                 System.Threading.Thread.Sleep(s);
55 
56                 se.Release();
57             }
58 
59             Console.WriteLine("{0}: END, threadid = {1}", name, System.Threading.Thread.CurrentThread.ManagedThreadId);
60         }
61     }
62 }
63 
64 //Thread A: COME IN, threadid = 3
65 //Thread B: COME IN, threadid = 4
66 //Thread B: START, threadid = 4
67 //Thread B: i = 0, sleep(795), threadid = 4
68 //Thread B: i = 1, sleep(200), threadid = 4
69 //Thread A: START, threadid = 3
70 //Thread A: i = 0, sleep(250), threadid = 3
71 //Thread B: i = 2, sleep(670), threadid = 4
72 //Thread A: i = 1, sleep(127), threadid = 3
73 //Thread B: i = 3, sleep(260), threadid = 4
74 //Thread A: i = 2, sleep(227), threadid = 3
75 //Thread B: i = 4, sleep(462), threadid = 4
76 //Thread A: i = 3, sleep(478), threadid = 3
77 //Thread B: i = 5, sleep(836), threadid = 4
78 //Thread A: i = 4, sleep(611), threadid = 3
79 //Thread B: i = 6, sleep(760), threadid = 4
80 //Thread A: i = 5, sleep(320), threadid = 3
81 //Thread B: i = 7, sleep(658), threadid = 4
82 //Thread A: i = 6, sleep(383), threadid = 3
83 //Thread B: i = 8, sleep(638), threadid = 4
84 //Thread A: i = 7, sleep(364), threadid = 3
85 //Thread B: i = 9, sleep(278), threadid = 4
86 //Thread B: END, threadid = 4
87 //Thread A: i = 8, sleep(89), threadid = 3
88 //Thread A: i = 9, sleep(192), threadid = 3
89 //Thread A: END, threadid = 3
90 //main end, mainthreadid = 1
91 //请按任意键继续. . .