Lazy initialization

var lazyFruit = new Lazy<Fruit>();
Fruit fruit = lazyFruit.Value;

using System;
using System.Collections;
using System.Collections.Generic;

public class Fruit
{
    private string _typeName;
    private static IDictionary<string, Fruit> _typesDictionary = new Dictionary<string, Fruit>();

    private Fruit(String typeName)
    {
        this._typeName = typeName;
    }

    public static Fruit GetFruitByTypeName(string type)
    {
        Fruit fruit;

        if (!_typesDictionary.TryGetValue(type, out fruit))
        {
            // Lazy initialization
            fruit = new Fruit(type);

            _typesDictionary.Add(type, fruit);
        }
        return fruit;
    }

    public static void ShowAll()
    {
        if (_typesDictionary.Count > 0)
        {
            Console.WriteLine("Number of instances made = {0}", _typesDictionary.Count);
            
            foreach (KeyValuePair<string, Fruit> kvp in _typesDictionary)
            {
                Console.WriteLine(kvp.Key);
            }
            
            Console.WriteLine();
        }
    }
    
    public Fruit()
    {
        // required so the sample compiles
    }
}

class Program
{
    static void Main(string[] args)
    {
        Fruit.GetFruitByTypeName("Banana");
        Fruit.ShowAll();

        Fruit.GetFruitByTypeName("Apple");
        Fruit.ShowAll();

        // returns pre-existing instance from first 
        // time Fruit with "Banana" was created
        Fruit.GetFruitByTypeName("Banana");
        Fruit.ShowAll();

        Console.ReadLine();
    }
}

namespace DesignPatterns.LazyInitialization;

public class LazyFactoryObject
{
    //internal collection of items
    //IDictionary makes sure they are unique
    private IDictionary<LazyObjectSize, LazyObject> _LazyObjectList =
        new Dictionary<LazyObjectSize, LazyObject>();

    //enum for passing name of size required
    //avoids passing strings and is part of LazyObject ahead
    public enum LazyObjectSize
    {
        None,
        Small,
        Big,
        Bigger,
        Huge
    }

    //standard type of object that will be constructed
    public struct LazyObject
    {
        public LazyObjectSize Size;
        public IList<int> Result;
    }

    //takes size and create 'expensive' list
    private IList<int> Result(LazyObjectSize size)
    {
        IList<int> result = null;

        switch (size)
        {
            case LazyObjectSize.Small:
                result = CreateSomeExpensiveList(1, 100);
                break;
            case LazyObjectSize.Big:
                result = CreateSomeExpensiveList(1, 1000);
                break;
            case LazyObjectSize.Bigger:
                result = CreateSomeExpensiveList(1, 10000);
                break;
            case LazyObjectSize.Huge:
                result = CreateSomeExpensiveList(1, 100000);
                break;
            case LazyObjectSize.None:
                result = null;
                break;
            default:
                result = null;
                break;
        }

        return result;
    }

    //not an expensive item to create, but you get the point
    //delays creation of some expensive object until needed
    private IList<int> CreateSomeExpensiveList(int start, int end)
    {
        IList<int> result = new List<int>();

        for (int counter = 0; counter < (end - start); counter++)
        {
            result.Add(start + counter);
        }

        return result;
    }

    public LazyFactoryObject()
    {
        //empty constructor
    }

    public LazyObject GetLazyFactoryObject(LazyObjectSize size)
    {
        //yes, i know it is illiterate and inaccurate
        LazyObject noGoodSomeOne;

        //retrieves LazyObjectSize from list via out, else creates one and adds it to list
        if (!_LazyObjectList.TryGetValue(size, out noGoodSomeOne))
        {
            noGoodSomeOne = new LazyObject();
            noGoodSomeOne.Size = size;
            noGoodSomeOne.Result = this.Result(size);

            _LazyObjectList.Add(size, noGoodSomeOne);
        }

        return noGoodSomeOne;
    }
}