public static void ResponseImageStream(Stream stream, string fileName)
        {
            if (stream.Length > 0)
            {
                try
                {
                    long fileSize = stream.Length;
                    System.Web.HttpContext.Current.Response.ContentType = "image/gif";
                    System.Web.HttpContext.Current.Response.AppendHeader("Content-Disposition", " attachment;filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
                    System.Web.HttpContext.Current.Response.AddHeader("Content-Length", fileSize.ToString());
                    byte[] fileBuffer = new byte[fileSize];
                    stream.Read(fileBuffer, 0, (int)fileSize);
                    stream.Close();
                    System.Web.HttpContext.Current.Response.BinaryWrite(fileBuffer);
                    System.Web.HttpContext.Current.Response.End();                }
                catch (Exception ex)
                {
                    throw;
                }
            }
        }没有下载到图片   都是把页面下载下来  高手看看这代码有没有错误