Mvc检查图片格式后上传

/// <summary>
        /// 检查是否文件是否图片并保存
        /// </summary>
        /// <param name="file">文件</param>
        /// <param name="savePath">保存文件的目录(例:/Img/Mark/)</param>
        /// <param name="newFileName">重命名后文件的名称</param>
        /// <returns>是否成功</returns>
        private bool SaveImage(HttpPostedFileBase file, string savePath, out string newFileName)
        {
            bool isSuc = false;
            newFileName = string.Empty;

            int contentLen = file.ContentLength;
            byte[] fileByte = new byte[2];
            using (Stream stream = file.InputStream)
            {
                stream.Read(fileByte, 0, 2);
                string fileFlag = string.Empty;
                if (fileByte != null && fileByte.Length > 0)
                {
                    fileFlag = fileByte[0].ToString() + fileByte[1].ToString();
                    Dictionary<string, string> dicImageByte = new Dictionary<string, string> {
                    { "255216","jpg"},{ "7173","gif"},{ "6677","bmp"},{ "13780","png"} };

                    string imageType = string.Empty;
                    bool isImage = dicImageByte.TryGetValue(fileFlag, out imageType);
                    if (isImage)
                    {
                        string fileName = Guid.NewGuid().ToString() + "." + imageType;
                        file.SaveAs(Path.Combine(Server.MapPath(savePath), fileName));
                        newFileName = savePath + fileName;
                        isSuc = true;
                    }
                }
                stream.Close();
                return isSuc;
            }
        }