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DnD Polyhedral Dice

A simple implementation of DnD dice mechanic.

This uses the FastRandom class which you can find on the linked page.


    using System.Collections.Generic;

namespace GameDice
	public enum DiceSides
		d4 = 4,
		d6 = 6,
		d8 = 8,
		d10 = 10,
		d12 = 12,
		d20 = 20

	public class DiceRoll
		FastRandom rand = new FastRandom();
		//The game uses polyhedral dice with different numbers of
		//sides.You can find dice like these in game stores and in
		//many bookstores.
		//In these rules, the different dice are referred to by the
		//letter d followed by the number of sides: d4, d6, d8, d10,
		//d12, and d20. For instance, a d6 is a six-sided die (the
		//typical cube that many games use).
		public int Roll(DiceSides side)
			return rand.Next((int)side);

		//Percentile dice, or d100, work a little differently.You
		//generate a number between 1 and 100 by rolling two
		//different ten-sided dice numbered from 0 to 9. One die
		//(designated before you roll) gives the tens digit, and
		//the other gives the ones digit.If you roll a 7 and a 1, for 
		//example, the number rolled is 71. Two 0s represent 100.
		//Some ten-sided dice are numbered in tens (00, 10, 20,
		//and so on), making it easier to distinguish the tens digit
		//from the ones digit.In this case, a roll of 70 and 1 is 71,
		//and 00 and 0 is 100.
		//When you need to roll dice, the rules tell you how many
		//dice to roll of a certain type, as well as what modifiers to
		//add. For example, “3d8 + 5” means you roll three eightsided dice, 
		//add them together, and add 5 to the total.
		//The same d notation appears in the expressions “1d3”
		//and “1d2.” To simulate the roll of 1d3, roll a d6 and divide
		//the number rolled by 2 (round up). To simulate the roll of
		//1d2, roll any die and assign a 1 or 2 to the roll depending
		//on whether it was odd or even. (Alternatively, if the number rolled is 
		//more than half the number of sides on the
		//die, it’s a 2.)
		public int PercentileRoll()
			var value1 = rand.Next(10);
			var value2 = rand.Next(10);
			if (value1 == 0 && value2 == 0) return 100;
			return value1 * 10 + value2;

	public enum Advantages

	public class D20
		DiceRoll dr = new DiceRoll();
		bool TestMode;

		public D20(bool testMode)
			TestMode = testMode;

		private int GetRandomNumber(bool firstNumber)
			if (TestMode)
				if (firstNumber)
					return 1;
					return 2;
			return dr.Roll(DiceSides.d20);

		public bool Roll(Advantages Advantage, List Modifiers, int targetNumber)
			int result;

			//1. Roll the die and add a modifier.Roll a d20 and add
			//the relevant modifier.This is typically the modifier derived from one of the six ability scores, and it sometimes
			//includes a proficiency bonus to reflect a character’s particular skill. (See chapter 1 for details on each ability and
			//how to determine an ability’s modifier.)
			result = GetRandomNumber(true);

			//Sometimes an ability check, attack roll, or saving throw
			//is modified by special situations called advantage and disadvantage. Advantage reflects the positive circumstances
			//surrounding a d20 roll, while disadvantage reflects the
			//opposite.When you have either advantage or disadvantage, you roll a second d20 when you make the roll. Use
			//the higher of the two rolls if you have advantage, and use
			//the lower roll if you have disadvantage. For example, if
			//you have disadvantage and roll a 17 and a 5, you use the
			//5.If you instead have advantage and roll those numbers,
			//you use the 17
			if (Advantage == Advantages.Advantage || Advantage == Advantages.Disadvantage)
				var result2 = GetRandomNumber(false);
				if (Advantage == Advantages.Advantage)
					if (result2 > result)
						result = result2;
					if (result2 < result)
						result = result2;

			//2. Apply circumstantial bonuses and penalties.A
			//class feature, a spell, a particular circumstance, or some
			//other effect might give a bonus or penalty to the check.
			foreach (var m in Modifiers)
				result += m;

			//3. Compare the total to a target number.If the total
			//equals or exceeds the target number, the ability check,
			//attack roll, or saving throw is a success. Otherwise, it’s a
			//failure.The DM is usually the one who determines target
			//numbers and tells players whether their ability checks,
			//attack rolls, and saving throws succeed or fail.
			if (result >= targetNumber)
				return true;
			return false;


About the author

Richard Brisley

I'm a multi-award winning Sitecore developer. Currently working for Sagittarius Marketing as a solutions architect to understand customer needs and produce multi-national high-performance websites.

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As a Tech Lead for Sagittarius marketing who I have been with for the last twelve years. I oversee a team of seven working pods, including numerous developers and contractors in multiple global locations. This involves supporting the developers with coding issues, meetings and phone calls with their clients and going out of pitches with potential new clients.

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