c# - 读取 WebException 的响应流

Question

我有以下方法，基本上是使用 Facebook 凭据对用户进行身份验证。出于某种原因，我在尝试处理授权 key (代码)时收到了 WebException。因此，我尝试读取响应流以了解发生了什么，但在读取流时我不断出错。这是我的代码:

    private void OnAuthCallback(HttpContextWrapper context, WebServerClient client)
    {
        try
        {
            IAuthorizationState authorizationState = client.ProcessUserAuthorization(context.Request);
            AccessToken accessToken = AccessTokenSerializer.Deserialize(authorizationState.AccessToken);
            String username = accessToken.User;
            context.Items[USERNAME] = username;
        }
        catch (ProtocolException e)
        {
            if (e.InnerException != null)
            {
                String message = e.InnerException.Message;
                if (e.InnerException is WebException)
                {
                    WebException exception = (WebException)e.InnerException;
                    var responseStream = exception.Response.GetResponseStream();
                    responseStream.Seek(0, SeekOrigin.Begin);
                    using (StreamReader sr = new StreamReader(responseStream))
                    {
                        message = sr.ReadToEnd();
                    }
                }
                EventLog.WriteEntry("OAuth Client", message);
            }
        }
    }

如果我删除 responseStream.Seek(0, SeekOrigin.Begin); 行，它会给我一个 ArgumentException 消息，指出流不可读。这条线就位后，它告诉我无法操作已经关闭的流。这个流是如何关闭的？为什么我不能从中读取？

Answer 1

您可以阅读响应的正文。我在 this answer 中找到了解决方案.

您应该将流转换为MemoryStream 并使用ToArray 方法，然后使用Encoding.UTF8.GetString 获取文本。

private void OnAuthCallback(HttpContextWrapper context, WebServerClient client)
{
    try
    {
        IAuthorizationState authorizationState = client.ProcessUserAuthorization(context.Request);
        AccessToken accessToken = AccessTokenSerializer.Deserialize(authorizationState.AccessToken);
        String username = accessToken.User;
        context.Items[USERNAME] = username;
    }
    catch (ProtocolException e)
    {
        if (e.InnerException != null)
        {
            String message = e.InnerException.Message;
            if (e.InnerException is WebException)
            {
                WebException exception = (WebException)e.InnerException;
                message = ExtractResponseString(webException);
            }
            EventLog.WriteEntry("OAuth Client", message);
        }
    }
}

public static string ExtractResponseString(WebException webException)
{
    if (webException == null || webException.Response == null)
        return null;

    var responseStream = 
        webException.Response.GetResponseStream() as MemoryStream;

    if (responseStream == null)
        return null;

    var responseBytes = responseStream.ToArray();
    var responseString = Encoding.UTF8.GetString(responseBytes);
    return responseString;
}