private static string EncryptDate(string d) { byte[] bytes = System.Text.Encoding.ASCII.GetBytes(d.ToString()); byte[] numArray = (new SHA256Managed()).ComputeHash(bytes); string str = string.Concat(d.ToString(), ";", PDFHelper.ByteArrayToString(numArray)); byte[] bytes1 = System.Text.Encoding.ASCII.GetBytes(str); char[] chrArray = new char[] { '=' }; return(Convert.ToBase64String(bytes1).TrimEnd(chrArray)); }