图片视频上传，下载方法

/// <summary>
/// 图片，视频，其他资源上传
/// </summary>
/// <param name="FileName,">文件名称</param>
/// <param name="typestyle">上传类型</param>
/// <param name="j">保存文件名随机数标识</param>
public static string FileUpdate(HttpFileCollection files, string FileName, int typestyle,int j)
{
if (FileName == null)
{
return string.Empty;
}
string fileExt = Path.GetExtension(FileName);
//读取存储路劲地址
string UploadPath = ConfigVal("UploadPath");
string path = null;
if (typestyle == 1)//图片上传
{
if (!(fileExt == ".jpg" || fileExt == ".jpeg" || fileExt == ".bmp" || fileExt == ".gif" || fileExt == ".png"))
{
return string.Empty;
}
path = string.Format("{0}/{1}{2}", UploadFolder(UploadType.PreImg), DateTime.Now.ToString("yyyyMMddHHmmssfff"), fileExt);
}
else if (typestyle == 2)//视频
{
if (!(fileExt == ".mp4" || fileExt == ".3gp" || fileExt == ".wmv" || fileExt == ".mpg" || fileExt == ".avi"))
{
//不是视频
return string.Empty;
}
path = string.Format("{0}/{1}{2}", UploadFolder(UploadType.Video), DateTime.Now.ToString("yyyyMMddHHmmssfff"), fileExt);
}
else
{
path = string.Format("{0}/{1}{2}", UploadFolder(UploadType.Resource), DateTime.Now.ToString("yyyyMMddHHmmssfff"), fileExt);
}

//3.获得网站的绝对路径 存储文件
string fileName = string.Format("{0}/{1}", UploadPath, path);
files[j].SaveAs(fileName);
return path;
}

 /// <summary>
        /// 文件下载
        /// </summary>
        /// <param name="url">图片网络地址</param>
        /// <param name="localfile">下载本地文件夹</param>
        /// <param name="filename">图片名称</param>
        /// <returns></returns>
        public static bool Download(string url, string localfile, string filename, string format=".pdf")
        {
            bool flag = false;
            if (url.Contains(",") || url.Contains("，") || filename.Contains("/"))
            {
                return flag;
            }
            try
            {
                ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3
                                       | SecurityProtocolType.Tls
                                       | (SecurityProtocolType)0x300 //Tls11
                                       | (SecurityProtocolType)0xC00; //Tls12

                HttpWebRequest request;
                if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
                {
                    ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                    request = WebRequest.Create(url) as HttpWebRequest;
                    request.ProtocolVersion = HttpVersion.Version10;
                }
                else
                {
                    request = WebRequest.Create(url) as HttpWebRequest;
                }

                request.Method = "GET";
                request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
                request.Headers.Add("Accept-Language", "zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3");
                request.UserAgent = "Mozilla/5.0 (Windows NT 5.2; rv:12.0) Gecko/20100101 Firefox/12.0";
                WebResponse response = request.GetResponse();
                //文件流获取图片操作
                Stream reader = response.GetResponseStream();
                string path = localfile + "/" + filename + format;        //图片路径命名 
                if (!System.IO.Directory.Exists(localfile))
                {
                    System.IO.Directory.CreateDirectory(localfile);
                }
                FileStream writer = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write);
                byte[] buff = new byte[512];
                int c = 0;                                           //实际读取的字节数   
                while ((c = reader.Read(buff, 0, buff.Length)) > 0)
                {
                    writer.Write(buff, 0, c);
                }
                //释放资源
                writer.Close();
                writer.Dispose();
                reader.Close();
                reader.Dispose();
                response.Close();
                //下载成功
                flag = true;
            }
            catch (Exception ex)
            {
                return false;
                throw ex;
            }
            return flag;
        }

        private static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
        {
            return true; //总是接受  
        }