C# Language Recursion in plain English


Recursion can be defined as:

A method that calls itself until a specific condition is met.

An excellent and simple example of recursion is a method that will get the factorial of a given number:

public int Factorial(int number)
    return number == 0 ? 1 : n * Factorial(number - 1);

In this method, we can see that the method will take an argument, number.

Step by step:

Given the example, executing Factorial(4)

  1. Is number (4) == 1?
  2. No? return 4 * Factorial(number-1) (3)
  3. Because the method is called once again, it now repeats the first step using Factorial(3) as the new argument.
  4. This continues until Factorial(1) is executed and number (1) == 1 returns 1.
  5. Overall, the calculation "builds up" 4 * 3 * 2 * 1 and finally returns 24.

The key to understanding recursion is that the method calls a new instance of itself. After returning, the execution of the calling instance continues.