流倒带问题

Question

因此，通过我的研究，我知道您需要"rewind" a stream 才能再次阅读它，或者您需要copy a stream。

我不能倒带这个流，所以我必须复制它。我尝试在下面这样做，但是当我从任一流中读取时，我最终读取了 0 个字节

CopyTo 的文档说它“读取流”。

这个“阅读”是否在最后设置了“阅读头”，还是我只是做错了什么？

    public static void ListenerCallback(IAsyncResult result)
    {
        HttpListener listener = (HttpListener)result.AsyncState;
        HttpListenerContext context = listener.EndGetContext(result);
        HttpListenerRequest request = context.Request;
        HttpListenerResponse response = context.Response;
        System.IO.Stream stream = new System.IO.MemoryStream();
        request.InputStream.CopyTo(stream);
        StreamReader reader = new StreamReader(stream);
        var res = reader.ReadToEnd(); //I should be seeing output here
        reader.Close();

        Console.WriteLine(res);
        NameValueCollection coll = HttpUtility.ParseQueryString(res);

        using (var outp = File.OpenWrite("output.pptx")) //This file should have data in it
        {
            request.InputStream.CopyTo(outp); 
        }

        response.StatusCode = 200;
        response.ContentType = "text/html";
        using (StreamWriter writer = new StreamWriter(context.Response.OutputStream, Encoding.UTF8))
            writer.WriteLine("File Uploaded");
        response.Close();
        stream.Close();
        request.InputStream.Close();

    }

Answer 1

如果您在此行之后的调试器中查看stream：

request.InputStream.CopyTo(stream);

您会看到它的位置在流的末尾。如果您在此行之后重置位置，您将按预期读取数据，假设流不为空：

request.InputStream.CopyTo(stream);
stream.Position = 0;    // Reset the position to the beginning
StreamReader reader = new StreamReader(stream);
var res = reader.ReadToEnd(); //I should be seeing output here
reader.Close();