.NET將關於多線程的功能定義在System.Threading名字空間中。因此，要使用多線程，必須先聲明引用此名字空間（using System.Threading;）。
即使你沒有編寫多線程應用程序的經驗，也可能聽說過“啟動線程”“殺死線程”這些詞，其實除了這兩個外，涉及多線程方面的還有諸如“暫停線程”“優先級”“掛起線程”“恢復線程”等等。下面將一個一個的解釋。
a.啟動線程
顧名思義，“啟動線程”就是新建並啟動一個線程的意思，如下代碼可實現：
Thread thread1 = new Thread(new ThreadStart( Count));
其中的 Count 是將要被新線程執行的函數。
b.殺死線程
“殺死線程”就是將一線程斬草除根，為了不白費力氣，在殺死一個線程前最好先判斷它是否還活著（通過 IsAlive 屬性），然後就可以調用 Abort 方法來殺死此線程。
c.暫停線程
它的意思就是讓一個正在運行的線程休眠一段時間。如 thread.Sleep(1000); 就是讓線程休眠1秒鐘。
d.優先級
這個用不著解釋了。Thread類中有一個ThreadPriority屬性，它用來設置優先級，但不能保證操作系統會接受該優先級。一個線程的優先級可 分為5種：Normal, AboveNormal, BelowNormal, Highest, Lowest。具體實現例子如下:
thread.Priority = ThreadPriority.Highest;
e.掛起線程
Thread類的Suspend方法用來掛起線程，知道調用Resume，此線程才可以繼續執行。如果線程已經掛起，那就不會起作用。
if (thread.ThreadState = ThreadState.Running)
{
thread.Suspend();
}
f.恢復線程
用來恢復已經掛起的線程，以讓它繼續執行，如果線程沒掛起，也不會起作用。
if (thread.ThreadState = ThreadState.Suspended)
{
thread.Resume();
}
下面將列出一個例子，以說明簡單的線程處理功能。此例子來自於幫助文檔。
using System;
using System.Threading;
// Simple threading scenario: Start a static method running
// on a second thread.
public class ThreadExample {
// The ThreadProc method is called when the thread starts.
// It loops ten times, writing to the console and yielding
// the rest of its time slice each time, and then ends.
public static void ThreadProc() {
for (int i = 0; i < 10; i++) {
Console.WriteLine("ThreadProc: {0}", i);
// Yield the rest of the time slice.
Thread.Sleep(0);
}
}
public static void Main() {
Console.WriteLine("Main thread: Start a second thread.");
// The constructor for the Thread class requires a ThreadStart
// delegate that represents the method to be executed on the
// thread. C# simplifies the creation of this delegate.
Thread t = new Thread(new ThreadStart(ThreadProc));
// Start ThreadProc. On a uniprocessor, the thread does not get
// any processor time until the main thread yields. Uncomment
// the Thread.Sleep that follows t.Start() to see the difference.
t.Start();
//Thread.Sleep(0);
for (int i = 0; i < 4; i++) {
Console.WriteLine("Main thread: Do some work.");
Thread.Sleep(0);
}
Console.WriteLine("Main thread: Call Join(), to wait until ThreadProc ends.");
t.Join();
Console.WriteLine("Main thread: ThreadProc.Join has returned. Press Enter to end program.");
Console.ReadLine();
}
}
此代碼產生的輸出類似如下內容：
Main thread: Start a second thread.
Main thread: Do some work.
ThreadProc: 0
Main thread: Do some work.
ThreadProc: 1
Main thread: Do some work.
ThreadProc: 2
Main thread: Do some work.
ThreadProc: 3
Main thread: Call Join(), to wait until ThreadProc ends.
ThreadProc: 4
ThreadProc: 5
ThreadProc: 6
ThreadProc: 7
ThreadProc: 8
ThreadProc: 9
Main thread: ThreadProc.Join has returned. Press Enter to end program.
