多线程锁读/写文本c#

Question

经过大量研究，阅读并尝试了这里的所有问题后，我认为是时候寻求帮助了。

我有一个 C# 应用程序，我正在尝试使用不同的线程写入相同的文件。

public static void LaunchThreads(string path_file)
{
    int i = 0;
    Dictionary<int, Thread> threadsdico = new Dictionary<int, Thread>();
    while (i < MAX_THREAD)
    {
            Thread thread = new Thread(() => ThreadEntryWriter(string path_file));
            thread.Name = string.Format("ThreadsWriters{0}", i);
            threadsdico.Add(i, thread);
            thread.Start();
            i++;
    }
    int zz = 0;
    while (zz < threadsdico.Count())
    {
        threadsdico[zz].Join();
        zz++;
    }
}
private static readonly Object obj = new Object();
public static void ThreadEntryWriter(string path_file)
{
    int w = 0;
    while (w < 99)
    {       
        string newline = w + " - test" + "\r";
        lock(obj)
        {
            string txt = File.ReadAllText(path_file);
            using (TextWriter myWriter = new StreamWriter(path_file))
            {   
                TextWriter.Synchronized(myWriter).Write(txt + newline);
            }
        }
        w++;
    }
}

我已经尝试了所有方法，我的代码在全局范围内都是这样的，但是我尝试了所有方法，每个锁，每个文件打开方法，但我不断收到The process cannot access the files because it's in use。产生此错误的行是using (TextWriter myWriter = new StreamWriter(path_file))。

我尝试了很多东西，关闭文件等，但是当线程同时开始工作时，程序停止并给我错误The process cannot access the files because it's in use（自我解释）。但我不明白为什么，锁是为了阻止另一个线程进入这里。我使用同步方法来编写线程安全的。抱歉写了这么长，这是我在这里的第一篇文章。

Answer 1

同步写入器仍需处理：

var newline = w + " - test";
using (var sw = new StreamWriter(path_file))
using (var sync = TextWriter.Synchronized(sw))
{
    // no need to add a new line char, just use other method to write
    sync.WriteLine(txt + newline);
}

另外，您可以保存一个sync 变量并从所有线程调用它的方法，它会为您完成所有工作，您可以在编写完所有文本后将其释放。

Answer 2

我测试了您的代码并应用了一些更改，它运行良好且没有错误。

我使用 winform 应用程序运行您的代码。请检查以下代码。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication14
{
    public partial class Form1 : Form
    {
        private readonly Object obj = new Object();

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
        }

        private void button1_Click(object sender, EventArgs e)
        {
            LaunchThreads("D:\\log.txt");
        }

        public void LaunchThreads(string path_file)
        {
            int i = 0;
            int MAX_THREAD = 10;
            Dictionary<int, Thread> threadsdico = new Dictionary<int, Thread>();
            while (i < MAX_THREAD)
            {
                Thread thread = new Thread(() => ThreadEntryWriter(path_file, string.Format("ThreadsWriters{0}", i)));
                    thread.Name = string.Format("ThreadsWriters{0}", i);
                    threadsdico.Add(i, thread);
                    thread.Start();
                    i++;
            }
            int zz = 0;
            while (zz < threadsdico.Count())
            {
                threadsdico[zz].Join();
                zz++;
            }
        }

        public void ThreadEntryWriter(string path_file,string threadName)
        {
            int w = 0;
            while (w < 99)
            {
                string newline = w + " - test" + " Thread:" + threadName + "\r\n";
                lock (obj)
                {
                    string txt = File.ReadAllText(path_file);
                    using (TextWriter myWriter = new StreamWriter(path_file))
                    {
                        TextWriter.Synchronized(myWriter).Write(txt + newline);
                    }
                }
                w++;
            }
        }
    }
}

我得到如下输出。

• 0 - 测试线程：ThreadsWriters1
• 0 - 测试线程：ThreadsWriters2
• 1 - 测试线程：ThreadsWriters2
• 2 - 测试线程：ThreadsWriters2
• 1 - 测试线程：ThreadsWriters1
• ....
• ....

Answer 3

您似乎想从多个线程向同一个文件写入行。

每次你想输出一行然后追加一行然后写出来的时候，读取所有的行是非常低效的。

我认为您的错误的原因是您没有处置 Synchronized TextWriter，因此即使您处置了底层 TextWriter，它也可能保持对文件的引用处于打开状态。

使用您自己的锁定和 Synchronized TextWriter 也是多余的。

我对您的代码进行了一些更改，以共享一个 Synchronized TextWriter 并仅追加行，而不是读取整个文件，追加然后将其写出：

    public static void LaunchThreads(string path_file)
    {
        int i = 0;
        using(var sw = File.CreateText(path_file))
        using(var syncWriter = TextWriter.Synchronized(sw)) 
        {
            Dictionary<int, Thread> threadsdico = new Dictionary<int, Thread>();
            while (i < MAX_THREAD)
            {
                Thread thread = new Thread(() => ThreadEntryWriter(syncWriter));
                thread.Name = string.Format("ThreadsWriters{0}", i);
                threadsdico.Add(i, thread);
                thread.Start();
                i++;
            }
            int zz = 0;
            while (zz < threadsdico.Count())
            {
                threadsdico[zz].Join();
                zz++;
            }
        }
    }

    public static void ThreadEntryWriter(TextWriter writer)
    {
        int w = 0;
        while (w < 99)
        {       
            writer.WriteLine($"{w} - test");
            w++;
        }
    }