MyList

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GenericListTest
{
    class GenericListTest
    {
        static void Main(string[] args)
        {
            //пробвай методите -> .AddElement            - добавя елемент на първото свободно място
            //                    .GetElementByValue     - връща елемента ако отговаря на стойността
            //                    .GetElementByIndex     - връща елемента на зададения индекс
            //                    .DeleteElementByIndex  - изтрива елемента на дадения индекс
            //                    .AddElementAtIndex     - добавя елемент на индекс
            //                    .ClearTheList          - изчиства листа и му връща оригиналния размер
            //                     .ExtractElements      - връща масив от елементите който си задал

            // в скобите задаваш оригиналния елемент на листа ако не зададеш автоматично се заделят 12 места
            GenericList<string> test = new GenericList<string>(3);

            test.AddElementAtIndex("Banam", 0);
            test.AddElementAtIndex("kenguru", 0);
            test.AddElementAtIndex("sega sym purvi", 1);
            test.AddElementAtIndex("iskam da sum posleden be", 3);
            test.AddElement("Ne az sym posleden");

            test.DeleteElementByIndex(5);

            foreach (string sentence in test.ExtractElements)
            {
                Console.WriteLine(sentence);
            }
        }
    }

    class GenericList<TElement>
    {
        private TElement[] allElements;
        private int sizeOfList;
        private int originalSizeOfTheList;
        private int currentIndex;

        public GenericList()
            : this (12)
        {

        }

        public GenericList(int sizeOfList)
        {
            this.originalSizeOfTheList = sizeOfList;
            this.sizeOfList = sizeOfList;
            this.currentIndex = 0;
            this.allElements = new TElement[sizeOfList];
        }

        public TElement[] ExtractElements { get { return this.allElements; } }

        public int LenghtOfList { get { return this.allElements.Length; } }

        public void AddElement(TElement element)
        {
            if (currentIndex == allElements.Length)
            {
                TElement[] arrayHolder = new TElement[sizeOfList];

                Array.Copy(allElements, arrayHolder, allElements.Length);

                sizeOfList *= 2;
                allElements = null;
                allElements = new TElement[sizeOfList];

                Array.Copy(arrayHolder, allElements, arrayHolder.Length);
            }

            allElements[currentIndex] = element;
            currentIndex++;
        }

        public TElement GetElementByValue(TElement elementSearched)
        {
            TElement elementToReturn = default(TElement);
            bool foundAnElement = false;
            for (int i = 0; i < allElements.Length; i++)
            {
                if (allElements[i] != null && allElements[i].Equals(elementSearched))
                {
                    elementToReturn = elementSearched;
                    foundAnElement = true;
                }
            }

            if (foundAnElement)
            {
                return elementToReturn;
            }
            else
            {
                throw new InvalidOperationException("No such element exists!!!");
            }
        }

        public TElement GetElementByIndex(int index)
        {
            if (index >= allElements.Length || index < 0)
            {
                throw new IndexOutOfRangeException("Invalid index entered!!!");
            }

            return allElements[index];
        }

        public void DeleteElementByIndex(int index)
        {
            if (index >= allElements.Length || index < 0)
            {
                throw new IndexOutOfRangeException("Invalid index entered!!!");
            }

            allElements[index] = default(TElement);

            for (int currIndex = index; currIndex < (allElements.Length - 1); currIndex++)
            {
                allElements[currIndex] = allElements[currIndex + 1];
            }

            currentIndex--;
            allElements[currentIndex] = default(TElement);
        }

        public void AddElementAtIndex(TElement element, int index)
        {
            if (index > allElements.Length || index < 0)
            {
                throw new IndexOutOfRangeException("Invalid index entered!!!");
            }

            if (currentIndex == allElements.Length || index == allElements.Length)
            {
                TElement[] arrayHolder = new TElement[sizeOfList];

                Array.Copy(allElements, arrayHolder, allElements.Length);

                sizeOfList *= 2;
                allElements = null;
                allElements = new TElement[sizeOfList];

                Array.Copy(arrayHolder, allElements, arrayHolder.Length);
            }

            for (int i = (allElements.Length - 1); i > index; i--)
            {
                allElements[i] = allElements[i - 1];
            }

            allElements[index] = default(TElement);
            allElements[index] = element;
            currentIndex++;
        }

        public void ClearTheList()
        {
            allElements = null;
            allElements = new TElement[originalSizeOfTheList];
        }
    }
}