Challenge

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

namespace Challenge1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.ForegroundColor = ConsoleColor.Green;
            Console.WriteLine("Welcome! Please Login");
            Login();
            Console.ReadKey();
        }
        static void Login()
        {
            Console.WriteLine("Username:");
            string username = Console.ReadLine();
            Console.WriteLine("Password:");
            string password = Console.ReadLine();
            if (username == "admin" && password == "123")
            {
                Console.WriteLine("Welcome back! " + username);
                Console.WriteLine("Check the available list of commands by typing 'commands'");
                string input = Console.ReadLine();
                switch (input)
                {
                    default:
                        Console.WriteLine("Oops! You entered a wrong command! Use 'commands' for help");
                        input = Console.ReadLine();
                        break;
                    case "commands":
                        Console.WriteLine("Available commands: adduser | addfile | showusers | showfiles | saveusers | savefiles | loadusers | loadfiles | exit");
                        input = Console.ReadLine();
                        break;
                    case "adduser":
                        Addusers();
                        break;
                    case "addfile":
                        Addfiles();
                        break;
                    case "showusers":
                        Showusers();
                        break;
                    case "showfiles":
                        Showfiles();
                        break;
                    case "deleteusers":
                        Deleteusers();
                        break;
                    case "deletefiles":
                        //code
                        break;
                    case "exit":
                        break;
                }
            } else
            {
                Console.WriteLine("You have entered a wrong Username or Password! Please try again");
                Login();
            }

        }
        static void Addusers()
        {
            Console.WriteLine("New Username:");
            string username = Console.ReadLine();
            Console.WriteLine("New Password for user " + username);
            string password = Console.ReadLine();
            string userdata = username + ";" + password;
            FileStream userfile = File.OpenWrite(AppDomain.CurrentDomain.BaseDirectory + "/users.txt");
            TextWriter writer = new StreamWriter(userfile);
            writer.WriteLine(userdata);
            writer.Flush();
            writer.Close();
            Console.WriteLine("User with Username: " + username + " and Password: " + password + " has been added Successfully!");
        }
        static void Addfiles()
        {
            Console.WriteLine("New FIle Name:");
            string filename = Console.ReadLine();
            Console.WriteLine("Contents of the new file named: " + filename);
            string contents = Console.ReadLine();
            string userdata = filename + ";" + contents;
            FileStream userfile = File.OpenWrite(AppDomain.CurrentDomain.BaseDirectory + "/files.txt");
            TextWriter writer = new StreamWriter(userfile);
            writer.WriteLine(userdata);
            writer.Flush();
            writer.Close();
            Console.WriteLine("File with Name: " + filename + " and Contents: " + contents + " has been added Successfully!");
        }
        static void Showusers() // Don't know how to make it loop not just read 1st line
        {
            Console.WriteLine("Opening users.txt Please wait...");
            Console.WriteLine("Users in Database:");
            FileStream userfile = File.OpenRead(AppDomain.CurrentDomain.BaseDirectory + "/users.txt");
            TextReader reader = new StreamReader(userfile);
            string userdata = reader.ReadLine();
            reader.Close();
            Console.WriteLine(userdata);
        }
        static void Showfiles() // Don't know how to make it loop not just read 1st line
        {
            Console.WriteLine("Opening files.txt Please wait...");
            Console.WriteLine("Files in Database:");
            FileStream userfile = File.OpenRead(AppDomain.CurrentDomain.BaseDirectory + "/files.txt");
            TextReader reader = new StreamReader(userfile);
            string userdata = reader.ReadLine();
            reader.Close();
            Console.WriteLine(userdata);
        }
        // Not working bellow!
        static void Deleteusers()
        {
            Console.WriteLine("The following users are present in the file: ");
            Showusers();
            Console.WriteLine("Enter the Username to be deleted:");
            string username = Console.ReadLine();
            FileStream userfile = File.OpenWrite(AppDomain.CurrentDomain.BaseDirectory + "/users.txt");
            TextWriter writer = new StreamWriter(userfile);
            writer.Close();
            // Missing code //
        }
    }
}