文件流生成文件

1.
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();
}
2.

using (FileStream fs = new FileStream(filePath, FileMode.Create))
{
fs.Write(b, 0, b.Length);
}

http://stackoverflow.com/questions/3434007/error-this-stream-does-not-support-seek-operations-in-c-sharp