using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Reflection;

​

namespace Example

{

    class Component {}

​

    class MySingleton : Component

    {

        static public MySingleton Instance = null;

    }

​

    class MyMistake : Component

    {

        public MyMistake Instance = null;

    }

​

    static class ExtensionMethods

    {

        public static bool TrySet_SingletonInstance<T>(this T c) where T : Component

        {

            var target = typeof(T).GetFields(BindingFlags.Static | BindingFlags.Public).SingleOrDefault(p => p.FieldType == typeof(T));

            if (target == null) return false;

            var oldValue = (T)target.GetValue(null);

            if (oldValue != null) return false;

            target.SetValue(null, c);

            return true;

        }

    }

​

    public class Program

    {

        static public void Main()

        {

            var singleton = new MySingleton();

            var ok = singleton.TrySet_SingletonInstance();

            Console.WriteLine(ok);

​

            var mistake = new MyMistake();

            var oops = mistake.TrySet_SingletonInstance();

            Console.WriteLine(oops);

        }

    }

}

​