Queue

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

namespace Queue
{
    internal class Program
    {
        static void Main(string[] args)
        {
            Queue<string> queue = new Queue<string>();
            queue.Enqueue("tom");
            queue.Enqueue("sam");
            queue.Enqueue("max");
            queue.Enqueue("kirill");
            foreach(string s in queue)
            {
                Console.WriteLine(s);
            }
            Console.WriteLine();
            string header = queue.First();
            Console.WriteLine($"первый элемент: {header}");
            Console.WriteLine();
            string firstitem = queue.Dequeue();
            Console.WriteLine($"извлеченный элемент: {firstitem}");
            Console.WriteLine();

            header = queue.First();
            Console.WriteLine($"первый элемент: {header}");
            Console.WriteLine();
            foreach(string s in queue)
            {
                Console.WriteLine(s);
            }
        }
        public class Node<T>
        {
            public Node(T data)
            {
                Data = data;
            }
            public T Data { get; set; }
            public Node<T> Next { get; set; }
        }
        public class Queue<T> : IEnumerable<T>
        {
            Node<T> head;
            Node<T> tail;
            int count;
            //добавление в очередь
            public void Enqueue(T data)
            {
                Node<T> node = new Node<T>(data);
                Node<T> tempnode = tail;
                tail = node;
                if (count == 0)
                {
                    head = tail;
                }
                else
                {
                    tempnode.Next = tail;

                }
                count++;
            }
            //удаление из очереди
            public T Dequeue()
            {
                if(count == 0)
                {
                    throw new InvalidOperationException("очередь пуста");
                }
                T output = head.Data;
                head = head.Next;
                count--;
                return output;
            }
            public T First
            {
                get
                {
                    if(IsEmpty)
                    {
                        throw new InvalidOperationException("очередь пуста");
                    }
                    return tail.Data;
                }
            }
            public int Count { get { return count; } }
            public bool IsEmpty { get { return count == 0; } }
            public void Clear()
            {
                head = tail = null;
                count = 0;
            }
            public bool Contains(T data)
            {
                Node<T> current = head;
                while (current != null)
                {
                    if (current.Data.Equals(data))
                    {
                        return true;
                    }
                    current = current.Next;
                }
                return false;
            }
            IEnumerator IEnumerable.GetEnumerator()
            {
                return ((IEnumerable)this).GetEnumerator();
            }
            IEnumerator<T> IEnumerable<T>.GetEnumerator()
            {
                Node<T> current = head;
                while(current != null)
                {
                    yield return current.Data;
                    current = current.Next;
                }
            }
        }
    }
}