C# IEnumerable<T>를 페이징 하는 확장 메서드

Page.cs

public struct Page<T> : IEnumerable<T>
{
    private IEnumerable<T> source;
    private IEnumerable<T> items;
    private int pageIndex;
    private int countPerPage;
    private int maxPage;

    public Page(IEnumerable<T> source, int pageIndex, int countPerPage)
    {
        this.source = source;
        this.items = source.Skip(pageIndex * countPerPage).Take(countPerPage);
        this.pageIndex = pageIndex;
        this.countPerPage = countPerPage;
        this.maxPage = (int)Math.Ceiling(source.Count() / (double)countPerPage);
    }

    public int PageIndex => pageIndex;
    public int PageNumber => pageIndex + 1;
    public int CountPerPage => countPerPage;
    public int MaxPage => maxPage;
    
    public bool IsFirstPage => PageIndex == 0;
    public bool IsLastPage => PageNumber == MaxPage;
    
    public Page<T> GetNextPage()
    {
        if (IsLastPage)
        {
            return this;
        }
        
        return new Page<T>(source, pageIndex + 1, countPerPage);
    }
    
    public Page<T> GetPrevPage()
    {
        if (IsFirstPage)
        {
            return this;
        }
        
        return new Page<T>(source, pageIndex - 1, countPerPage);
    }

    public IEnumerator<T> GetEnumerator()
    {
        return items.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return items.GetEnumerator();
    }
}

PaginationExtensions.cs

public static class PaginationExtensions
{
    public static IEnumerable<Page<T>> GetPages<T>(this IEnumerable<T> source, int countPerPage)
    {
        return Enumerable.Range(0, source.GetPageCount(countPerPage)).Select(index => new Page<T>(source, index, countPerPage));
    }

    public static Page<T> GetPage<T>(this IEnumerable<T> source, int currentPage, int countPerPage)
    {
        return new Page<T>(source, currentPage, countPerPage);
    }
    
    public static int GetPageCount<T>(this IEnumerable<T> source, int countPerPage)
    {
        return (int)Math.Ceiling(source.Count() / (double)countPerPage);
    }
}

Program.cs

namespace CSharp
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Item> items = new List<Item>()
            {
                new Item("1", 10),
                new Item("2", 1),
                new Item("3", 1),
                new Item("4", 1),
                new Item("5", 1),
                new Item("6", 106),
                new Item("7", 1),
                new Item("8", 1),
                new Item("9", 1),
                new Item("0", 1),
                new Item("1", 10),
                new Item("2", 1),
                new Item("3", 1),
                new Item("4", 1),
                new Item("5", 1),
                new Item("6", 106),
                new Item("7", 1),
                new Item("8", 1),
                new Item("9", 1),
                new Item("0", 1),
                new Item("1", 10),
                new Item("2", 1),
                new Item("3", 1),
                new Item("4", 1),
                new Item("5", 1),
                new Item("6", 106),
                new Item("7", 1),
                new Item("8", 1),
                new Item("9", 1),
                new Item("0", 1),
                new Item("1", 10),
                new Item("2", 1),
                new Item("3", 1),
                new Item("4", 1),
                new Item("5", 1),
                new Item("6", 106),
                new Item("7", 1),
                new Item("8", 1),
                new Item("9", 1),
                new Item("0", 1),
            };
            
            foreach (var page in items.GetPages(countPerPage: 9))
            {
                Console.WriteLine($"Page - {page.PageNumber} -");

                foreach (var item in page)
                {
                    Console.WriteLine($"{item.name}:{item.stack}");
                }

                Console.WriteLine();
            }
        }
    }
}