Time for another quiz for you all, this is just a micro-benchmark so we want to be careful not to conclude too much but it's useful for understanding the costs and their origins.    Consider the two snippets shown below:

            // choice #1, using Generics

            int total = 0;

            List<int> li = new List<int>();

            for (i = 0; i < 20; i++)
                li.Add(i);

            // start timer

            for (i = 0; i < 10000000; i++)
                foreach (int el in li)
                    total += el;

            // end timer


            // choice #2, using ArrayList

            ArrayList al = new ArrayList();

            for (i = 0; i < 20; i++)
                al.Add(i);

            // start timer

            for (i = 0; i < 10000000; i++)
                foreach (int el in al)
                    total += el;

            // end timer

Now try to answer these question (no peeking at the comments until you've done your work :))

Q1: Which is faster?

Q2: How much faster?

Q3: Why is it faster?

Q4: What price do we pay for this speed?  Quantify it if you can.

Answers and discussion soon :)