mshak

internal static class UnsafeNativeMethods
{
    [DllImport("shell32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    internal static extern void SHChangeNotify(uint wEventId, uint uFlags, IntPtr dwItem1, IntPtr dwItem2);
}

public class FileExtensionRegistrator
{
	public const string fileExtension = ".bla";
	public const string keyName = "bla_bla_file";
	public const string fileDescription = "It is my BLA file";

	public static void SetAssociation(string openWith)
	{
		SetAssociation(fileExtension, keyName, openWith, fileDescription);
	}

	public static void SetAssociation(string extension, string keyName, string openWith, string fileDescription)
	{
		RegistryKey baseKey;
		RegistryKey openMethod;
		RegistryKey shell;
		RegistryKey currentUser;

		baseKey = Registry.ClassesRoot.CreateSubKey(extension);
		baseKey.SetValue("", keyName);

		openMethod = Registry.ClassesRoot.CreateSubKey(keyName);
		openMethod.SetValue("", fileDescription);
		openMethod.CreateSubKey("DefaultIcon").SetValue("", "\"" + openWith + "\",0");
		shell = openMethod.CreateSubKey("Shell");
		shell.CreateSubKey("open").CreateSubKey("command").SetValue("", string.Format("\"{0}\" -cmd=open -file=\"%1\"",openWith));
		baseKey.Close();
		openMethod.Close();
		shell.Close();

		// Delete the key instead of trying to change it
		currentUser = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\FileExts\\" + extension, true);
		if (currentUser != null)
		{
			currentUser.DeleteSubKey("UserChoice", false);
			currentUser.Close();
		}
		// Tell explorer the file association has been changed
		UnsafeNativeMethods.SHChangeNotify(0x08000000, 0x0000, IntPtr.Zero, IntPtr.Zero);
	}

	public static void RemoveAssociation()
	{
		RemoveAssociation(fileExtension, keyName);
	}

	public static void RemoveAssociation(string extension, string keyName)
	{
		try
		{
			Registry.ClassesRoot.DeleteSubKeyTree(extension);
			Registry.ClassesRoot.DeleteSubKeyTree(keyName);
		}
		catch {}

		// Tell explorer the file association has been changed
		UnsafeNativeMethods.SHChangeNotify(0x08000000, 0x0000, IntPtr.Zero, IntPtr.Zero);
	}
}

FileExtensionRegistrator.SetAssociation(Application.ExecutablePath);

using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace XmlSerializeDemo
{
    [XmlRoot("TechTree")]
    public class TechCollection
    {
        [XmlAttribute("version")]
        public int Version { get; set; }

        [XmlElement("Tech")]
        public TechItem Item { get; set; }
    }

    public class TechItem
    {
        [XmlAttribute("type")]
        public string Type { get; set; }

        [XmlAttribute("name")]
        public string Name { get; set; }
    }

    internal class Program
    {
        private static void Main(string[] args)
        {
            var e = new TechItem() { Type = "Noraml", Name = "Age 1" };
            var t = new TechCollection() { Version = 5, Item = e };

            Serialize(@".\demo.xml", t);
        }

        private static void Serialize<T>(string path, T obj)
        {
            XmlSerializer serializer = new XmlSerializer(obj.GetType());
            XmlWriterSettings settings = new XmlWriterSettings();
            settings.ConformanceLevel = ConformanceLevel.Document;
            settings.OmitXmlDeclaration = false; // не подавлять xml заголовок
            settings.Encoding = Encoding.UTF8; // кодировка
            settings.Indent = true; // добавлять отступы
            settings.IndentChars = "    "; // сиволы отступа

            // подавляем неймспейсы
            XmlSerializerNamespaces dummyNSs = new XmlSerializerNamespaces();
            dummyNSs.Add(string.Empty, string.Empty);

            using (FileStream fileStream = new FileStream(path, FileMode.Create))
            {
                using (XmlWriter xw = XmlWriter.Create(fileStream, settings))
                {
                    serializer.Serialize(xw, obj, dummyNSs);
                }
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<TechTree version="5">
    <Tech type="Noraml" name="Age 1" />
</TechTree>

using System.IO;
using System.Text;
using System.Xml;
using System.Xml.Serialization;

namespace XmlSerializeDemo
{
    [XmlRoot("TechTree")]
    public class Tech
    {
        [XmlAttribute("version")]
        public int Version { get; set; }

        [XmlElement("Info")]
        public string Description { get; set; }
    }

    internal class Program
    {
        private static void Main(string[] args)
        {
            var t = new Tech() { Version = 5, Description = "I'm xml" };
            Serialize(@".\demo.xml", t);
        }

        private static void Serialize<T>(string path, T obj)
        {
            XmlSerializer serializer = new XmlSerializer(obj.GetType());
            XmlWriterSettings settings = new XmlWriterSettings();
            settings.ConformanceLevel = ConformanceLevel.Document;
            settings.OmitXmlDeclaration = false; // не подавлять xml заголовок
            settings.Encoding = Encoding.UTF8; // кодировка
            settings.Indent = true; // добавлять отступы
            settings.IndentChars = "    "; // сиволы отступа

            // подавляем неймспейсы
            XmlSerializerNamespaces dummyNSs = new XmlSerializerNamespaces();
            dummyNSs.Add(string.Empty, string.Empty);

            using (FileStream fileStream = new FileStream(path, FileMode.Create))
            {
                using (XmlWriter xw = XmlWriter.Create(fileStream, settings))
                {
                    serializer.Serialize(xw, obj, dummyNSs);
                }
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<TechTree version="5">
    <Info>I'm xml</Info>
</TechTree>