Stream转MemoryStream解决Stream.Length报错此流不支持查找操作

1.StreamToMemoryStream

 MemoryStream StreamToMemoryStream(Stream instream)
        {
            MemoryStream outstream = new MemoryStream();
            const int bufferLen = 4096;
            byte[] buffer = new byte[bufferLen];
            int count = 0;
            while ((count = instream.Read(buffer, 0, bufferLen)) > 0)
            {
                outstream.Write(buffer, 0, count);
            }
            return outstream;
        }

2.Stream.Length报错:此流不支持查找

                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url + (data == "" ? "" : "?" + data));
                request.Method = "GET";
                using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
                {
                    if (response.StatusCode == HttpStatusCode.OK)
                    {                       
                        Stream rs =response.GetResponseStream();                                  
                        
                        var ms = StreamToMemoryStream(rs);
                        ms.Seek(0, SeekOrigin.Begin);                        int buffsize =(int)ms.Length; //rs.Length 此流不支持查找,先转为MemoryStream
                        byte[] bytes = new byte[buffsize];

                        ms.Read(bytes, 0, buffsize);
                        ms.Flush();ms.Close();
　　　　　　　　　　　　　　rs.Flush();rs.Close();
                }

From:http://www.cnblogs.com/xuejianxiyang/p/5816684.html