HTMLManager.cs

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

namespace ConsoleApp1.HTML
{
    class HTMLManager
    {
        public string CreateHTML(string templateHTML, string[] userNameArray)
        {
            string html = File.ReadAllText(templateHTML);
            html = html.Replace("{USERARRAY}", UserHTML(userNameArray));
            html = html.Replace("{USERSUM}", userNameArray.Length.ToString());

            //File.WriteAllText("test.txt", text);
            Console.WriteLine("HTML Composed");
            return html;

        }

        private string UserHTML(string[] userNameArray)
        {
            string userHTML = "";
            List<string> userNames = new List<string>();
            for(int i = 0; i < userNameArray.Length; i++)
            {
                userNames.Add("<tr>" +
                    "<td>" + userNameArray[i] + "</td>" +
                    "<td>" + userNameArray[i] + "</td>" +
                    "</tr>" + "\n");
            }

            userHTML = string.Join("", userNames);
            Console.WriteLine("UserHTML Complete");
            return userHTML;
        }

    }
}