C#

class CryptoStreamEncryption
    {
        private static byte[] Key = ASCIIEncoding.ASCII.GetBytes(Constants.Misc.MyKey);
        private static byte[] IV = ASCIIEncoding.ASCII.GetBytes(Constants.Misc.MyKey);

        public static void Encrypt(XmlDocument ThisDocument, string FullPath)
        {
            try
            {
                FileStream fStream = File.Open(FullPath, FileMode.Create);
                Rijndael RijndaelAlg = Rijndael.Create();
                CryptoStream cStream = new CryptoStream(fStream, RijndaelAlg.CreateEncryptor(Key, IV), CryptoStreamMode.Write);
                StreamWriter sWriter = new StreamWriter(cStream);
                try
                {
                    sWriter.WriteLine(ThisDocument.OuterXml);
                }
                catch (Exception e)
                {
                    Console.WriteLine("An error occurred: {0}", e.Message);
                }
                finally
                {
                    sWriter.Close();
                    cStream.Close();
                    fStream.Close();
                }
            }
            catch (CryptographicException e)
            {
                Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
            }
            catch (UnauthorizedAccessException e)
            {
                Console.WriteLine("A file error occurred: {0}", e.Message);
            }

        }

        public static XmlDocument Decrypt(string FullPath)
        {
            XmlDocument ThisDocument = new XmlDocument();
            string val = null;
            try
            {
                FileStream fStream = File.Open(FullPath, FileMode.Open);
                Rijndael RijndaelAlg = Rijndael.Create();
                CryptoStream cStream = new CryptoStream(fStream, RijndaelAlg.CreateDecryptor(Key, IV), CryptoStreamMode.Read);
                StreamReader sReader = new StreamReader(cStream);
                try
                {
                    val = sReader.ReadLine();
                }
                catch (Exception e)
                {
                    Console.WriteLine("An error occurred: {0}", e.Message);
                }
                finally
                {
                    sReader.Close();
                    cStream.Close();
                    fStream.Close();
                }
            }
            catch (CryptographicException e)
            {
                Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
            }
            catch (UnauthorizedAccessException e)
            {
                Console.WriteLine("A file error occurred: {0}", e.Message);
            }
            catch (System.IO.FileLoadException e)
            {
                Console.WriteLine("A file load error occurred: {0}", e.Message);
            }
            catch (System.IO.FileNotFoundException e)
            {
                Console.WriteLine("A file not found error occurred: {0}", e.Message);
            }
            if (!(val == null))
            {
                ThisDocument.LoadXml(val);
            }
            return ThisDocument;
        }
    }

using System.Reflection;
using System.Runtime.InteropServices;
...
object[] res = Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(GuidAttribute), true);
string guid = null;
if (res.Length > 0)
    guid = ((GuidAttribute)res[0]).Value;

public static void Encrypt(XmlDocument ThisDocument, string targetFile) {
    FileStream outFile = new FileStream(targetFile, FileMode.OpenOrCreate, FileAccess
        .Write, FileShare.None, 0x1000, FileOptions.Encrypted| FileOptions.SequentialScan);
    ThisDocument.Save(outFile);
    outFile.Close();
}
public static XmlDocument Decrypt(string sourceFile) {
    FileStream inFile = new FileStream(sourceFile, FileMode.Open, FileAccess
        .Read, FileShare.None, 0x1000, FileOptions.Encrypted | FileOptions.SequentialScan);
    ThisDocument.Save(outFile);
    inFile.Close();
}