验证上传文件真实格式

        /// <summary>
        /// 验证上传文件真实格式
        /// </summary>
        /// <param name="fileUpload"></param>
        /// <returns></returns>
        private bool ValidationFile(HttpPostedFile fileUpload)
        {
            HttpPostedFile file = fileUpload;
            BinaryReader r = new BinaryReader(fileUpload.InputStream);
            string bx = " ";
            byte buffer;
            try
            {
                buffer = r.ReadByte();
                bx = buffer.ToString();
                buffer = r.ReadByte();
                bx += buffer.ToString();
            }
            catch (Exception)
            {
                Response.Write("文件格式错误！");
                Response.End();
            }

            bool isok = false;
            foreach (int item in Enum.GetValues(typeof(FileExtension)))
            {
                if (item.ToString() == bx)
                {
                    isok = true;
                    break;
                }
            }

            return isok;
        }

        /// <summary>
        /// 上传文件的真实格式
        /// </summary>
        public enum FileExtension          
        {
            JPG = 255216,
            GIF = 7173,
            BMP = 6677,
            PNG = 13780
            //COM = 7790,
            //EXE = 7790,
            //DLL = 7790,
            //RAR = 8297,
            //ZIP = 8075,
            //XML = 6063,
            //HTML = 6033,
            //ASPX = 239187,
            //CS = 117115,
            //JS = 119105,
            //TXT = 210187,
            //SQL = 255254,
            //BAT = 64101,
            //BTSEED = 10056,
            //RDP = 255254,
            //PSD = 5666,
            //PDF = 3780,
            //CHM = 7384,
            //LOG = 70105,
            //REG = 8269,
            //HLP = 6395,
            //DOC = 208207,
            //XLS = 208207,
            //DOCX = 208207,
            //XLSX = 208207,
           //txt:4950
        }