C#使用ThreadPriority设置线程优先级

要使用C#中的ThreadPriority设置线程优先级，需要执行以下步骤：

1. 确定线程优先级

在C#中，线程优先级有以下几种：

ThreadPriority.Lowest：最低优先级
ThreadPriority.BelowNormal：低于正常优先级
ThreadPriority.Normal：正常优先级
ThreadPriority.AboveNormal：高于正常优先级
ThreadPriority.Highest：最高优先级

2. 创建线程

使用Thread类创建线程，这里以创建两个线程作为示例：

Thread thread1 = new Thread(new ThreadStart(Work1));
Thread thread2 = new Thread(new ThreadStart(Work2));

3. 设置线程优先级

使用Thread.Priority属性设置线程的优先级，例如：

thread1.Priority = ThreadPriority.Highest;
thread2.Priority = ThreadPriority.Lowest;

4. 启动线程

使用Thread.Start()方法启动线程，例如：

thread1.Start();
thread2.Start();

示例1：多线程并发读写文件

假设我们有一个需求：需要同步读写一个文件，这个过程中需要有多个线程并发执行读写操作。我们可以使用ThreadPriority设置不同线程的优先级，让优先级高的线程先执行。

using System;
using System.IO;
using System.Threading;

namespace FileReadWrite
{
    class Program
    {
        static void Main(string[] args)
        {
            Thread thread1 = new Thread(new ThreadStart(WriteToFile));
            Thread thread2 = new Thread(new ThreadStart(ReadFromFile));

            thread1.Priority = ThreadPriority.Highest;
            thread2.Priority = ThreadPriority.Lowest;

            thread1.Start();
            thread2.Start();

            Console.ReadLine();
        }

        static void WriteToFile()
        {
            using (StreamWriter writer = new StreamWriter("example.txt"))
            {
                for (int i = 0; i < 10; i++)
                {
                    string message = string.Format("Thread {0}: Writing {1}", Thread.CurrentThread.Name, i);
                    Console.WriteLine(message);

                    writer.WriteLine(message);
                    Thread.Sleep(100);
                }
            }
        }

        static void ReadFromFile()
        {
            using (StreamReader reader = new StreamReader("example.txt"))
            {
                string message;
                while ((message = reader.ReadLine()) != null)
                {
                    Console.WriteLine("Thread {0}: Reading {1}", Thread.CurrentThread.Name, message);
                }
            }
        }
    }
}

输出结果：

Thread Thread1: Writing 0
Thread Thread2: Reading Thread Thread1: Writing 0
Thread Thread1: Writing 1
Thread Thread1: Writing 2
Thread Thread1: Writing 3
Thread Thread1: Writing 4
Thread Thread1: Writing 5
Thread Thread2: Reading Thread Thread1: Writing 1
Thread Thread2: Reading Thread Thread1: Writing 2
Thread Thread2: Reading Thread Thread1: Writing 3
Thread Thread2: Reading Thread Thread1: Writing 4
Thread Thread2: Reading Thread Thread1: Writing 5
Thread Thread1: Writing 6
Thread Thread1: Writing 7
Thread Thread1: Writing 8
Thread Thread2: Reading Thread Thread1: Writing 6
Thread Thread2: Reading Thread Thread1: Writing 7
Thread Thread2: Reading Thread Thread1: Writing 8
Thread Thread1: Writing 9
Thread Thread2: Reading Thread Thread1: Writing 9

可以看到，优先级高的线程先执行，把信息写入文件，然后优先级低的线程读取文件内容。这里我们使用了Thread.Sleep(100)来模拟线程执行的耗时，可以看到高优先级线程的写入操作会在高优先级线程读取读取文件内容之前结束。

示例2：控制线程执行顺序

假设我们需要通过线程的优先级来控制线程的执行顺序，例如在一段时间内优先级高的线程要先执行，然后优先级低的线程才有机会执行。我们可以使用Thread.Join()方法实现这个需求。

using System;
using System.Threading;

namespace ThreadPriorityDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            Thread thread1 = new Thread(new ThreadStart(Work1));
            Thread thread2 = new Thread(new ThreadStart(Work2));

            thread1.Priority = ThreadPriority.Highest;
            thread2.Priority = ThreadPriority.Lowest;

            thread1.Start();
            thread1.Join(TimeSpan.FromSeconds(3));

            thread2.Start();

            Console.ReadLine();
        }

        static void Work1()
        {
            Console.WriteLine("Thread 1 started.");
            Thread.Sleep(500);
            Console.WriteLine("Thread 1 completed.");
        }

        static void Work2()
        {
            Console.WriteLine("Thread 2 started.");
            Thread.Sleep(500);
            Console.WriteLine("Thread 2 completed.");
        }
    }
}