流倒带问题

Question

所以，通过我的研究，我知道你需要在再次读取之前"倒带"一个流，或者你需要复制一个流。

我不能倒带这个流，所以我必须复制它。我试着在下面这样做，但是当我从任何一个流中读取时，我最终读取0字节

CopyTo的文档说它"读取流"。

这个"阅读"设置"读头"在最后，还是我只是做了别的什么错误?

    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

如果您在调试器中查看stream，在这行之后:

request.InputStream.CopyTo(stream);

你会看到它的位置在流的末尾。如果您在这行之后重置位置，您将按照预期读取数据，假设流不是空的:

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();