Lesson 15.1 – Getting random numbers for the game

Lesson Objectives

At the end of this lesson, you will know…

• How to create random numbers – the easy way, and the good way

This game, like many games, needs to get random numbers.

We’ll use random numbers to determine how much damage a player does to a monster, how much damage the monster does to the player, and which items from the monster loot table the player will receive after defeating a monster.

However, there is something important that you need to consider when using random numbers.

The .Net framework has a built-in random number generating class, called “Random”. Unfortunately, it doesn’t produce numbers that are really random. In a simple game like this, that’s not a big problem. But if you were serious about building a good game, you’d want to use a better technique.

The problem with better technique is that it uses some complex objects and logic to generate the random numbers. These are way more complex than I can describe in a tutorial for beginners. In fact, some of the things in it are difficult for advanced programmers to understand.

So, if you want to use the better version, you’ll just have to take my word that it works.

I have both versions below. You can select either one to use in your version of the game.

Creating a random number generator

Step 1: Start Visual Studio Express 2013 for Desktop, and open the solution.

Step 2: Right-click on the Engine project and add a new class named RandomNumberGenerator.cs.

Step 3: Decide which method you want to use, and paste the code below into the RandomNumberGenerator class.

The code for the easy way:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace Engine
{
    public static class RandomNumberGenerator
    {
        private static Random _generator = new Random();
 
        public static int NumberBetween(int minimumValue, int maximumValue)
        {
            return _generator.Next(minimumValue, maximumValue + 1);
        }
    }
}

In the simple version, we create a Random object (_generator) and use its Next() method to get a random value between the minimum and maximum values passed in as parameter.

The code for the more random way:

using System;
using System.Security.Cryptography;
namespace Engine
{
    // This is the more complex version
    public static class RandomNumberGenerator
    {
        private static readonly RNGCryptoServiceProvider _generator = new RNGCryptoServiceProvider();
        public static int NumberBetween(int minimumValue, int maximumValue)
        {
            byte[] randomNumber = new byte[1];
            _generator.GetBytes(randomNumber);
            double asciiValueOfRandomCharacter = Convert.ToDouble(randomNumber[0]);
            // We are using Math.Max, and substracting 0.00000000001,
            // to ensure "multiplier" will always be between 0.0 and .99999999999
            // Otherwise, it's possible for it to be "1", which causes problems in our rounding.
            double multiplier = Math.Max(0, (asciiValueOfRandomCharacter / 255d) - 0.00000000001d);
            // We need to add one to the range, to allow for the rounding done with Math.Floor
            int range = maximumValue - minimumValue + 1;
            double randomValueInRange = Math.Floor(multiplier * range);
            return (int)(minimumValue + randomValueInRange);
        }
    }
}

In this version, we use an instance of an encryption class (RNGCryptoServiceProvider). This class is better at not following a pattern when it creates random numbers. But we need to do some more math to get a value between the passed in parameters.

Summary

Now you can create random numbers in the game.

We only use random numbers in a few places, in this simple version of the game. However, if you want to add more features, you may find this useful.

Source code for this lesson

Source code on GitHub

Source code on Dropbox

NOTE: This has the code for both versions of the class, the simple one and the complex one. Only create one RandomNumberGenerator class and copy the code from the one version that you want to use.

Next lesson: Lesson 16.1 – Writing the function to move the player

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