private static string GetFileMD5(string filePath)

        {

            string _md5Value = string.Empty;

            try

            {

                if (System.IO.File.Exists(filePath))

                {

                    FileStream file = new FileStream(filePath, FileMode.Open);

                    System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();

                    byte[] retVal = md5.ComputeHash(file);

                    file.Close();

                    file.Dispose();

                    _md5Value= BitConverter.ToString(retVal).Replace("-", "");

                }

                return _md5Value;

            }

            catch (Exception ex)

            {

                //throw new Exception(string.Format("GetFileMD5_Error_{0}_{1}", DateTime.Now, ex.Message));

                return _md5Value;

            }

        }