C#

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();
}