问题描述
我正在尝试使用 byte 流从 url 获取图像.但我收到此错误消息:
I'm trying to get an image from an url using a byte stream. But i get this error message:
此流不支持搜索操作.
这是我的代码:
byte[] b; HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(url); WebResponse myResp = myReq.GetResponse(); Stream stream = myResp.GetResponseStream(); int i; using (BinaryReader br = new BinaryReader(stream)) { i = (int)(stream.Length); b = br.ReadBytes(i); // (500000); } myResp.Close(); return b;
伙计们,我做错了什么?
What am i doing wrong guys?
推荐答案
您可能想要这样的东西.要么检查长度失败,要么 BinaryReader 在幕后进行搜索.
You probably want something like this. Either checking the length fails, or the BinaryReader is doing seeks behind the scenes.
HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(url); WebResponse myResp = myReq.GetResponse(); byte[] b = null; using( Stream stream = myResp.GetResponseStream() ) using( MemoryStream ms = new MemoryStream() ) { int count = 0; do { byte[] buf = new byte[1024]; count = stream.Read(buf, 0, 1024); ms.Write(buf, 0, count); } while(stream.CanRead && count > 0); b = ms.ToArray(); }
我使用反射器检查过,是对 stream.Length 的调用失败了.GetResponseStream 返回一个 ConnectStream,并且该类的 Length 属性会引发您看到的异常.正如其他发布者所提到的,您无法可靠地获得 HTTP 响应的长度,因此这是有道理的.
I checked using reflector, and it is the call to stream.Length that fails. GetResponseStream returns a ConnectStream, and the Length property on that class throws the exception that you saw. As other posters mentioned, you cannot reliably get the length of a HTTP response, so that makes sense.