No errors in Visual Studio, Code Executes but something not right C# (updated! problem in String.Insert)

Question

I'm writing a program for schoolwork, that's supposed to generate a 10 000 "movie" list. A single "movie" consist of a string in a form "moviename year director". I say "movie" because movie name and director are supposed to be randomly generated with letters from a-z.

I wrote the following logic to generate one such "movie". Movie name and director are random letter combination in length between 4-10 charachters. Code gives no errors in visual studio, executes, but shows blank. If I wrote correctly, then this code should generate one such string and print it, yet console is blank.

Do while loop is there to check if, however unlikely, there is a double item in the List (this is for when I do the 10 000 version).

In short, I dont understand what am I doing wrong?

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

namespace Experiment
{
  class Program
  {
    static void Main(string[] args)
    {
        Movies();
        Console.ReadKey();
    }

    public static void Movies()
    {
        List<string> movieList = new List<string>();
        bool check = false;

        do
        {
            string movie = "";

            for (int i = 0; i < GetNum(); i++)
            {
                movie.Insert(0, Convert.ToString(GetLetter()));
            }

            movie.Insert(0, " ");
            movie.Insert(0, Convert.ToString(GetYear()));
            movie.Insert(0, " ");

            for (int i = 0; i < GetNum(); i++)
            {
                movie.Insert(0, Convert.ToString(GetLetter()));
            }

            if (movieList.Contains(movie))
            {
                check = false;
            }
            else
            {
                movieList.Add(movie);
                check = true;
            }

        } while (check == false);

        Console.WriteLine(movieList[0]);


    }


    public static Random _random = new Random();

    public static char GetLetter()
    {
        int num = _random.Next(0, 26);
        char let = (char)('a' + num);
        return let;
    }

    public static int GetNum()
    {
        int num = _random.Next(4, 11);
        return num;
    }

    public static int GetYear()
    {
        int num = _random.Next(1920, 2020);
        return num;
    }

   }
 }

Answer 1

Strings are immutable, so calling the Insert() method on the movie string doesn't do anything to the current movie variable. Instead it returns the new string.

You are however better off changing the movie type from string to StringBuilder, which is a dynamically allocated buffer of characters, so your example becomes:

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

namespace sotest
{
    class Program
    {
        static void Main(string[] args)
        {
            Movies();
            Console.ReadKey();
        }

        public static void Movies()
        {
            List<string> movieList = new List<string>();
            bool check = false;

            do
            {
                StringBuilder movie = new StringBuilder();

                for (int i = 0; i < GetNum(); i++)
                {
                    movie.Insert(0, Convert.ToString(GetLetter()));
                }

                movie.Insert(0, " ");
                movie.Insert(0, Convert.ToString(GetYear()));
                movie.Insert(0, " ");

                for (int i = 0; i < GetNum(); i++)
                {
                    movie.Insert(0, Convert.ToString(GetLetter()));
                }

                if (movieList.Contains(movie.ToString()))
                {
                    check = false;
                }
                else
                {
                    movieList.Add(movie.ToString());
                    check = true;
                }

            } while (check == false);

            Console.WriteLine(movieList[0]);


        }


        public static Random _random = new Random();

        public static char GetLetter()
        {
            int num = _random.Next(0, 26);
            char let = (char)('a' + num);
            return let;
        }

        public static int GetNum()
        {
            int num = _random.Next(4, 11);
            return num;
        }

        public static int GetYear()
        {
            int num = _random.Next(1920, 2020);
            return num;
        }

    }
}