C# 为什么这个异步程序不交错输出？_C#_Multithreading_Asynchronous_Async Await_Threadpool

C# 为什么这个异步程序不交错输出？

c# multithreading asynchronous

C# 为什么这个异步程序不交错输出？,c#,multithreading,asynchronous,async-await,threadpool,C#,Multithreading,Asynchronous,Async Await,Threadpool,下面的异步程序读取两个文件，每行的第一个字符从n=1增加到63，并打印文件中的每一行。打印是在DisplayResult方法中完成的我希望输出是交错的，因为两个异步方法ProcessReadWriteAsync是并行启动的。但是，输出不是如下所示的交错看起来两个或多个DisplayResult方法不能同时运行，但为什么会有几个非后台线程准备好执行它们，而主非后台线程在等待任务ProcessReadWriteAsync完成时没有执行任何操作 public static async Task M

下面的异步程序读取两个文件，每行的第一个字符从n=1增加到63，并打印文件中的每一行。打印是在DisplayResult方法中完成的

我希望输出是交错的，因为两个异步方法ProcessReadWriteAsync是并行启动的。但是，输出不是如下所示的交错

看起来两个或多个DisplayResult方法不能同时运行，但为什么会有几个非后台线程准备好执行它们，而主非后台线程在等待任务ProcessReadWriteAsync完成时没有执行任何操作

public static async Task Main()
        {
            Task task1 = ProcessReadWriteAsync(@"/tmp/temp1Write.txt");

            Task task2 = ProcessReadWriteAsync(@"/tmp/temp2Write.txt");

            await task1;
            await task2;
        }

        public static async Task ProcessReadWriteAsync(string filePath)
        {
            try
            {
            await ReadWriteAsync(filePath);

            } catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            } finally
            {
                Console.WriteLine();
            }
        }

        public static async Task ReadWriteAsync(string path, string text)
        {
            FileStream stream = new FileStream(path, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite, 4096, useAsync: true);

                byte[] buffer = new byte[0x1000];

                int noOfCharactersRead = await stream.ReadAsync(buffer, 0, buffer.Length);

                DisplayResult(buffer: buffer);
        }

        public static async Task ReadWriteAsync(string path)
        {
            await ReadWriteAsync(path, "");
        }

        private static void DisplayResult(byte[] buffer)
        {
            string DecodedText = Encoding.UTF8.GetString(buffer, 0, buffer.Length);

            string[] strings = DecodedText.Split('\n');

            for (int index = 0; index < strings.Length;index++)
            {
                Console.WriteLine(strings[index]);
            }
        }

更新：

我将函数DisplayResult更改为async，并在ReadWriteAsync中等待它，正如我预期的那样，输出现在是交错的，如下所示：

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因此，我认为一个非后台线程执行DisplayResult的两个调用是正确的，因此为什么第二个DisplayResult调用在第一个调用完成之前被阻止，但我不确定为什么只有一个非后台线程可用？

这是一个磁盘操作。磁盘操作本质上是磁盘绑定的，而不是CPU绑定的。必须进行一点多任务处理，因为这项操作需要很长时间。但平行化不会有帮助，更可能是有害的

对一个旋转磁盘的不同部分抛出一堆请求是一种巨大的资源浪费——基本上，整个驱动器花费更多的时间移动读取头，然后实际读取。因此，有这样的功能将把它整理成一个有用的顺序读取。很可能这个功能——或者类似的功能——检测出你试图遵循的坏主意。试着把它挽救到一个合理的程度

我喜欢说“多任务处理必须仔细挑选问题”。如果不这样做，那么最终的代码将比基本的顺序代码更需要内存，更复杂（因此更容易出错），最糟糕的是速度更慢。磁盘和网络是这些情况的极端例子。

如果使用

任务，是否会得到相同的行为。运行调用ProcessReadWriteAsync
？有可能I/O实际上正在完成synchronously@KevinGosseTask.Run
将委托作为参数，我不知道如何使用委托，因此无法对其进行测试。然而，我从IDE的描述中对Task.Run
的理解是，它与调用异步方法的作用相同，换句话说，它允许同步方法作为异步方法运行？我已经更新了我的问题，等待异步DisplayResult时的输出正如我所期望的那样是交错的，因此行为不同。您将什么更改为使DisplayResultasync？我也无法重现您所描述的内容。在不更改代码的情况下，我得到了交错输出。（我使用了一个带有.NETCore3.1的控制台应用程序）@TheodorZoulias done。谢谢你的提示。我希望现在看起来更简单。好的，很高兴知道，但是我只对打印发生在哪里以及为什么只有一个非后台线程执行它感兴趣。磁盘绑定
1. msdn.microsoft.com/library/hh191443.aspx                83732
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