Today I was reading some book on the .net development and found there interesting thing.

Guy explains “Why to use Generics?“
He wrote that Frameworks 1.0 and 1.1 did not support Generics, so developers were using Object.
He says, that generics offers two significant advantages over using the Object class:
1) Reduced run-time errors
That is because type-safety.
2) Improved perfomance
Casting requires boxing and unboxing, which slows performance. Using of Generics doesn’t require casting or boxing, which improves run-time performance.

And then funny thing…
He put a box which looks like:

Real Word
(his name)
I haven’t been able to reproduce the performance benefits of generics;
however, according to Microsoft, generics are faster than using
casting. In practice, casting proved to be several times faster than
using a generic. However, you probably won’t notice performance
differences in your applications. (My tests over 100,000 iterations took only a few seconds.) So you should still use generics because they are type-safe.

OMG! I could not believe in his words. As per me this should be BULLSHIT, unless I 100% missed something there.

Test

I wrote a really quick verification like:

namespace TestGenericsPerfomance
{
    class Program
    {
        internal static void Main(string[] args)
        {
            Stopwatch stopWatch = new Stopwatch();
            //Working with value objects
            //Generic wins 100%
            stopWatch.Start();
            ArrayList nonGenericArrayList = new ArrayList();
            for (int i = 0; i < 10000000; i++)
            {
                nonGenericArrayList.Add(i);//takes Object so boxing is performed here…
            }
            stopWatch.Stop();
            Console.WriteLine(string.Format(“Int32: ArrayList (boxing): {0:0}”, stopWatch.Elapsed.TotalMilliseconds));
            stopWatch.Restart();
            List<Int32> someCustomersIds = new List<Int32>();
            for (int i = 0; i < 10000000; i++)
            {
                someCustomersIds.Add(i);
            }
            stopWatch.Stop();
            Console.WriteLine(string.Format(“Int32: List<Int32> (generic): {0:0}”, stopWatch.Elapsed.TotalMilliseconds));
 
            //Working with reference objects
            //Generic still wins, but not so sure..
            Customer sharedCustomer = new Customer();
            stopWatch.Restart();
            ArrayList nonGenericArrayListCustomers = new ArrayList();
            for (int i = 0; i < 10000000; i++)
            {
                nonGenericArrayListCustomers.Add(sharedCustomer);//no boxing.. jut putting the same reference
            }
            stopWatch.Stop();
            Console.WriteLine(string.Format(“Customer: ArrayList (no boxing): {0:0}”, stopWatch.Elapsed.TotalMilliseconds));
            stopWatch.Restart();
            List<Customer> genericBasedOnInterface = new List<Customer>();
            for (int i = 0; i < 10000000; i++)
            {
                genericBasedOnInterface.Add(sharedCustomer);//just put the same reference in generic list
            }
            stopWatch.Stop();
            Console.WriteLine(string.Format(“Customer: List<Customer> (no boxing): {0:0}”, stopWatch.Elapsed.TotalMilliseconds));
        }
        private class Customer
        {
            public string Name = “Andriy Buday”;
            public string Buy(string what)
            {
                return “I’m glad I bought that.”;
            }
        }
    }
}

And the result is:

Int32: ArrayList (boxing): 2443
Int32: List<Int32> (generic): 294
Customer: ArrayList (no boxing): 586
Customer: List<Customer> (no boxing): 315
Press any key to continue . . .

As you see generics are much faster. Also I searched over internet and found a lot of different stuff that says that generics provide better performance.

My Opinion

You would said what kind of book do I read. Is it “C# for Complete Dummy“?
No, that is Microsoft’s training Kit for exam 70-536.
Even if this was a book “C# for Dummy” it should not contain mistakes. And even if this is a book for kids it should not contain wrong thing. Yea.. it could be very simple, but not wrong!

I thought to write e-mail to that guy, but then decided that there is no need in this.

Just be careful when you read books and others thoughts, even mine :)

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