Visual Studio Add-in for testing regular expressions

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Configuration.Install;
using System.Linq;
using System.Reflection;
using System.IO;
using System.Xml;
using System.Windows.Forms;


namespace RegexTester
{
    /// <summary>
    /// Installs the Regular Expression Tester.
    /// </summary>
    [RunInstaller(true)]
    public partial class RegexTesterInstaller : System.Configuration.Install.Installer
    {
        public RegexTesterInstaller()
        {
            InitializeComponent();
        }

        private string GetAddInXmlPath()
        {
            return Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.CommonApplicationData),
                @"Microsoft\MSEnvShared\Addins\RegularExpressionEvaluator.AddIn");
        }

        public override void Install(System.Collections.IDictionary stateSaver)
        {
            string assemblyPath = base.Context.Parameters["AssemblyPath"];
            string addinXmlPath = GetAddInXmlPath();

            Stream addInStream = Assembly.GetExecutingAssembly().GetManifestResourceStream("RegexTester.RegexTester.AddIn");
            XmlDocument doc = new XmlDocument();
            doc.Load(addInStream);
            XmlNamespaceManager nameSpaceManager = new XmlNamespaceManager(doc.NameTable);
            nameSpaceManager.AddNamespace("addin", "http://schemas.microsoft.com/AutomationExtensibility");
            XmlNode node = doc.SelectSingleNode("/addin:Extensibility/addin:Addin/addin:Assembly", nameSpaceManager);
            node.InnerText = assemblyPath;
            string directoryName = Path.GetDirectoryName(addinXmlPath);
            if (!Directory.Exists(directoryName))
            {
                Directory.CreateDirectory(directoryName);
            }
            using (FileStream fs = new FileStream(addinXmlPath, FileMode.Create, FileAccess.Write, FileShare.Write))
            {
                XmlWriterSettings settings = new XmlWriterSettings();
                settings.Indent = true;
                settings.Encoding = System.Text.Encoding.UTF8;
                XmlWriter writer = XmlWriter.Create(fs, settings);
                doc.WriteTo(writer);
                writer.Flush();
                writer.Close();
            }
            base.Install(stateSaver);
        }

        private void DeleteAddInFile()
        {
            string file = GetAddInXmlPath();
            if (File.Exists(file))
            {
                File.Delete(file);
            }
        }

        public override void Uninstall(IDictionary savedState)
        {
            DeleteAddInFile();

            base.Uninstall(savedState);
        }

        public override void Rollback(IDictionary savedState)
        {
            DeleteAddInFile();

            base.Rollback(savedState);
        }
    }
}