C# ViewState Management/Storage - Four Locations!

using System;
using System.Collections;
namespace StaticAppGlobals
{
    public class AppGlobal
    {
        private static volatile AppGlobal instance = null;
        private static object syncRoot = new object();
        // make the default constructor private, we never
        // explicitly create an instance with "new"
        private AppGlobal()
        {
        }
        // public property that gets the single instance of this class.
        public static AppGlobal Instance
        {
            get
            {
                // only create a new instance if one doesn't already exist.
                if (instance == null)
                {
                    // use lock to ensure that only one thread can access
                    // this block of code at once. You can invoke lock on anything,
                    // syncRoot is just a convenience object instance.
                    lock (syncRoot)
                    {
                        if (instance == null)
                            instance = new AppGlobal();
                    }
                }
                return instance;
            }
        }
        private static string mySampleProperty = String.Empty;
        public static string MySampleProperty
        {
            get { return mySampleProperty; }
            set { mySampleProperty = value; }
        }

        public static Hashtable MySettings = new Hashtable();
    }
}