What is recursion and when should I use it?

Answer 1

Recursion is solving a problem with a function that calls itself. A good example of this is a factorial function. Factorial is a math problem where factorial of 5, for example, is 5 * 4 * 3 * 2 * 1. This function solves this in C# for positive integers (not tested - there may be a bug).

public int Factorial(int n)
{
    if (n <= 1)
        return 1;

    return n * Factorial(n - 1);
}