this List<string> ListName as a parameter?

Question

What does it mean when you have a this List as a parameter to a method?

public static void KillZombies(this List<Zombie> ZombiesToKill, int NumberOfBullets)
{
    ...
}

Answer 1

That would mean that the method is an Extension Method:

The code calling the method might look a little confusing:

var zombies = new List<Zombie>();
zombies.KillZombies(15);

In reality, this is a kind of syntactic sugar which is equivalent to:

public static void KillZombies(List<Zombie> zombiesToKill,
                               int numberOfBullets)
{
    // Code here
}

With the calling code looking like:

var zombies = new List<Zombie>();
KillZombies(zombies, 15);