ASP.NET 实现Base64文件流下载PDF

 //Base64文件流 
            byte[] buffer = Convert.FromBase64String(decodedString); 
            System.IO.Stream iStream = new System.IO.MemoryStream(buffer);
            try
            {
                int length;
                long dataToRead;
                string filename = sn + ".pdf";//保存的文件名称
                dataToRead = iStream.Length;
                Response.Clear();
                Response.ClearHeaders();
                Response.ClearContent();
                Response.ContentType = "application/pdf"; //文件类型  
                Response.AddHeader("Content-Length", dataToRead.ToString());//添加文件长度，进而显示进度  
                Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));
                while (dataToRead > 0)
                {
                    if (Response.IsClientConnected)
                    {
                        length = iStream.Read(buffer, 0, 10000);
                        Response.OutputStream.Write(buffer, 0, length);
                        Response.Flush();
                        buffer = new Byte[10000];
                        dataToRead = dataToRead - length;
                    }
                    else
                    {
                        dataToRead = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                Response.Write("文件下载时出现错误!");
            }
            finally
            {
                if (iStream != null)
                {
                    iStream.Close();
                }
                //结束响应，否则将导致网页内容被输出到文件，进而文件无法打开   
                Response.Flush();
                Response.End();

            }