DateTime.AddDays() not working as expected

I have this simple program:

        DateTime aux = new DateTime(2012, 6, 12, 12, 24, 0);
        DateTime aux2 = new DateTime(2012, 6, 12, 13, 24, 0);
        aux2.AddDays(1);

       Console.WriteLine((aux2 - aux).TotalHours.ToString());

        Console.ReadLine();

I debugged this and found aux2.AddDays(1); doesn't seem to work, what am I missing here? it should return 25 but the answer is one.

What is the problem?

also AddHours doesn't work, I guess that the others aren't working too.

It does work but you don't do anything with the return value, try

aux2 = aux2.AddDays(1);

DateTimes share this facet of immutability with Strings.

EDIT

There is a little paragraph about it on MSDN

This method does not change the value of this DateTime. Instead, it returns a new DateTime whose value is the result of this operation.

DateTime.AddDays returns new DateTime that adds specified number of days. You need to assign it to your variable:

aux2 = aux2.AddDays(1);