[C#] C# Random Object

Date: 2023.04.16 Updated: 2023.04.16

Categories: CS

Tags: Random

📋 This is my note-taking from what I learned in the class “Programming 1 - COMP 100-002”

C# Random Object

What is an object?

An object is a piece of software that can do things (has methods attached to it).
It is created by the new operator from a template (class).
C# comes with tons of templates (Random, DateTime, String, …).
Each of the object that is created from these templates has its own set of methods.
Some objects even have data values attached to them.

Creating the Random object

//This should be declared in global scope
static Random rand = new Random();
//c.f static int[] age = new int[34];

//Using a seed gives the same set of random values
//This is important if your set of values needs to be reproduced
static Random rand = new Random(54321);

Using the Next() method of the random object

The following show the various use of the random object:

//returns an int less than the largest int (2^31 - 1)
rand.Next();

//returns an int less than the value of max_number
rand.Next(max_number);

//returns an int greater or equal to the min_number and less than max_number
rand.Next(min_number, max_number);

Using the NextDouble() method of the random object

//returns a double in the range 0.0 to 1.0 not including 1.0
rand.NextDouble();

//returns a double in the range 0.0 to 10.0 not including 10.0
10 * rand.NextDouble();

//returns a double in the range 30.0 to 35.0 not including 35.0
30 + 5 * rand.NextDouble();

Example using random numbers

//create the random object
static Random rand = new Random();

//declare and allocate for 100 int element
int[] numbers = new int[100];

//loop to set each item to a random value
for(int i = 0; i < 100; i++)
{
  numbers[i] = rand.Next(10, 20);
}

Example using random characters

//create the random object
static Random rand = new Random();

//declare and allocate for 100 int element
char[] letters = new char[100];

//loop to set each item to a random value
for(int i = 0;i < 100;i++)
{
  letters[i] = (char)rand.Next('A', 'Z');
}

Example building random sentences

//declare the source of my random names
string[] names = {"Bart", "Arya", "Curt", "Eden", "Fred", "Gina", "Jack", "Dave", "Kate"};

//declare the source of my random pets
string[] pets = {"dog", "cat", "hamster", "parrot", "buggie", "spider", "rabbit", "snake"};

//declare the resulting sentences
string[] result = new string[10];

//loop to build the sentences
for(int i = 0; i < result.Length; i++)
{
  string name = names[rand.Next(names.Length)];
  string pet = pets[rand.Next(pets.Length)];
  int age = rand.Next(5, 10);
  result[i] = $"{name} is my pet {pet}. He is {age} months old.";
}

Summary

An object is a piece of software that has methods and values
A random object may be create with or without a seed
The random object may be used to generate random values (ints, chars, doubles, strings, sentences …)
The random object can be used to create interesting programs.

Seyeon