来自HttpWebResponse的Stream的奇怪行为

Question

I experienced some strange issue while reading stream from HttpWebResponse. In case of successful response (200 status code) I get exception when access to Length property of stream. But in case of WebException when server returns some error (eg BadRequest) everything is perfect, Length works ok. I can get ContentLength directly from HttpWebResponse but want to know the reason of such behavior. Here is debug screenshot of both cases

        try
        {
            var request = (HttpWebRequest) WebRequest.Create(uriString);
            request.Method = HttpMethod.Get.Method;
            request.ContentType = "application/json";
            response = (HttpWebResponse) request.GetResponse();
            statusCode = response.StatusCode;
            responseString = DecodeResponse(response);
        }
        catch (WebException ex)
        {
            response = (HttpWebResponse) ex.Response;
            responseString = DecodeResponse(response);
            statusCode = response.StatusCode;
        }

        private static string DecodeResponse(HttpWebResponse response)
        {
            byte[] data;
            using (Stream stream = response.GetResponseStream())
            {
                data = new byte[stream.Length];
                stream.Read(data, 0, data.Length);
            }
            return Encoding.UTF8.GetString(data);
        }

Answer 1

The stream (ConnectStream) which is being created internally as part of the response does not support the Length property. Different streams support different properties depending on their implementation.

You could use a different way to read from the stream as in this post:

C# How do i convert System.Net.ConnectStream to a byte[] (array)