如何使静态类线程安全？

Question

我有一个简单的静态日志记录类。但是，它肯定不是线程安全的，因为每个调用都试图写入同一个文件。我得到了这些例外情况：

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) 
...

什么是最好的方法使它的线程安全？

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);
    }
}

作为一个日志记录函数，我希望能够从代码的许多不同部分访问它（因此，我选择它为静态的原因）。然而，我想要使它成为线程安全的，我总是必须向它传递一个公共对象来lock（），我认为这违背了静态函数的目的。还是事实并非如此？

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);
        }
    }
}