Question

我有一个简单的简单日志类，它是静态的。但是，它绝对不是线程安全的，因为每次调用都会尝试写入同一个文件。我得到以下例外：

The process cannot access the file 'logfile.txt' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath) 
...

使线程安全的最佳方法是什么？

public static class Logger
{
    private static readonly string LOG_FILENAME = "logfile.txt";
    private static readonly string LOG_FOLDER = System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "App name");
    private static readonly string LOG_FULLPATH = System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "App name", LOG_FILENAME);

    public static void LogMessageToFile(string msg)
    {
        msg = string.Format("{0:G}: {1}{2}", DateTime.Now, msg, Environment.NewLine);
        File.AppendAllText(LOG_FULLPATH, msg);
    }
}

作为日志记录功能，我希望能够从我的代码的许多不同部分访问它（因此，为什么我选择它作为静态）。但是，我想象的是为了使它成为线程安全的，我总是要将它传递给lock（）on一个常见的对象，我认为这违背了静态函数的目的。或者情况不是这样吗？

Answer 1

public static class Logger
{
    private static readonly string LOG_FILENAME = "logfile.txt";
    private static readonly string LOG_FOLDER = System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "App name");
    private static readonly string LOG_FULLPATH = System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "App name", LOG_FILENAME);

    private static Object theLock=new Object();

    public static void LogMessageToFile(string msg)
    {
        msg = string.Format("{0:G}: {1}{2}", DateTime.Now, msg, Environment.NewLine);
        lock (theLock)
        {
            File.AppendAllText(LOG_FULLPATH, msg);
        }
    }
}

Answer 2

在LogMessageToFile方法中，您需要一个锁来阻止多线程访问：

private static Object _mylock = new Object();
public static void LogMessageToFile(string msg)
{
    lock(_mylock)
    {
       msg = string.Format("{0:G}: {1}{2}", DateTime.Now, msg, Environment.NewLine);
       File.AppendAllText(LOG_FULLPATH, msg);
    }
}

如何使静态类线程安全？

2 个答案: