Chapter 11 Sorting Question

coronoahcoro · May 4th, 2012, 09:24 AM

In chapter 11, there is a Try It Out section about using Sorting with IComparable.

Below is the line that called the sorting method

Code:

Console.WriteLine("People sorted with default comparer (by age):");
list.Sort();

When I debugged it, that line goes to CompareTo method just like the book explained, but I don't understand how the CompareTo method ended up sorting the ArrayList. I just do not see how this happens even after I debug the code. Can anyone explain why the code below works to sort the ArrayList? I do not see that the code change the position of the items in the ArrayList.

Code:

public int CompareTo(object obj)
    {
      if (obj is Person)
      {
        Person otherPerson = obj as Person;
        return this.Age - otherPerson.Age;
      }
      else
      {
        throw new ArgumentException("Object to compare to is not a Person object.");
      } 
    }