using System; using System.Collections.Generic; using System.Text; public interface IWebPageElement { string Render(); } public class Header : IWebPageElement { private string text; public Header(string text) { this.text = text; } public string Render() { return $"

{text}

"; } } public class Paragraph : IWebPageElement { private string text; public Paragraph(string text) { this.text = text; } public string Render() { return $"

{text}

"; } } public class ListElement : IWebPageElement { private List items; public ListElement(List items) { this.items = items; } public string Render() { StringBuilder itemsStr = new StringBuilder(); foreach (var item in items) { itemsStr.Append($"

{item}

"); } return $"

{itemsStr}"; } } public class WebPage { private string title; private List elements; public WebPage(string title) { this.title = title; this.elements = new List(); } public void AddElement(IWebPageElement element) { elements.Add(element); } public string Display() { StringBuilder elementsStr = new StringBuilder(); foreach (var element in elements) { elementsStr.AppendLine(element.Render()); } return $"\n\n {title}\n\n\n\n {elementsStr}\n\n"; } } public class Program { public static void Main(string[] args) { WebPage page = new WebPage("My Web Page"); page.AddElement(new Header("Welcome to My Web Page")); page.AddElement(new Paragraph("This is a paragraph of text on the web page.")); List items = new List { "Item 1", "Item 2", "Item 3" }; page.AddElement(new ListElement(items)); Console.WriteLine(page.Display()); /* Outputs: My Web Page

Welcome to My Web Page

This is a paragraph of text on the web page.

Item 1
Item 2
Item 3

*/ } }