如何使用.NET打开文件以进行非独占写访问

Question

是否可以在.NET中使用非独占写访问权限打开文件？如果是这样,怎么样？我希望有两个或更多进程同时写入同一个文件.

编辑:这是这个问题的上下文:我正在为IIS编写一个简单的日志记录HTTPModule.由于在不同应用程序池中运行的应用程序作为不同的进程运行,我需要一种在进程之间共享日志文件的方法.我可以编写一个复杂的文件锁定例程,或者一个懒惰的编写器,但这是一个丢弃的项目,所以它并不重要.

这是我用来计算过程的测试代码.

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Threading;

namespace FileOpenTest
{
    class Program
    {
        private static bool keepGoing = true;

        static void Main(string[] args)
        {
            Console.CancelKeyPress += new ConsoleCancelEventHandler(Console_CancelKeyPress);

            Console.Write("Enter name: ");
            string name = Console.ReadLine();
            //Open the file in a shared write mode
            FileStream fs = new FileStream("file.txt", 
                                           FileMode.OpenOrCreate, 
                                           FileAccess.ReadWrite, 
                                           FileShare.ReadWrite);

            while (keepGoing)
            {
                AlmostGuaranteedAppend(name, fs);
                Console.WriteLine(name);
                Thread.Sleep(1000);
            }

            fs.Close();
            fs.Dispose();
        }

        private static void AlmostGuaranteedAppend(string stringToWrite, FileStream fs)
        {
            StreamWriter sw = new StreamWriter(fs);

            //Force the file pointer to re-seek the end of the file.
            //THIS IS THE KEY TO KEEPING MULTIPLE PROCESSES FROM STOMPING
            //EACH OTHER WHEN WRITING TO A SHARED FILE.
            fs.Position = fs.Length;

            //Note: there is a possible race condition between the above
            //and below lines of code. If a context switch happens right
            //here and the next process writes to the end of the common
            //file, then fs.Position will no longer point to the end of
            //the file and the next write will overwrite existing data.
            //For writing periodic logs where the chance of collision is
            //small, this should work.

            sw.WriteLine(stringToWrite);
            sw.Flush();
        }

        private static void Console_CancelKeyPress(object sender, ConsoleCancelEventArgs e)
        {
            keepGoing = false;
        }
    }
}

Answer 1

使用File.Open打开文件时使用FileShare枚举.具体来说,使用FileShare.ReadWrite.

Answer 2

FileStream类有一个构造函数,它包含多个选项,包括FileShare

new FileStream(filePath, FileMode.Create, FileAccess.ReadWrite, FileShare.ReadWrite);