http://stackoverflow.com/questions/27176159/performance-type-derived-from-generic

PerformanceProblemWithNestedClass.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;

namespace PerformanceProblem
{
    public class Program
    {
        public static void Main()
        {
            Measure(new DerivedClass());
            Measure(new BaseClass<object>());
        }

        private static void Measure(BaseClass<object> baseClass)
        {
            var sw = Stopwatch.StartNew();
            baseClass.Run();
            sw.Stop();
            Console.WriteLine(sw.ElapsedMilliseconds);
        }
    }

    public class DerivedClass : BaseClass<object>
    {
    }

    public class BaseClass<T>
    {
        private List<T> _list = new List<T>();

        public BaseClass()
        {
            Enumerable.Empty<T>();
            // or Enumerable.Repeat(new T(), 10);
            // or even new T();
            // or foreach (var item in _list) {}
        }

        public void Run()
        {
            for (var i = 0; i < 8000000; i++)
            {
                if (_list.Any())
                // or if (_list.Count() > 0)
                // or if (_list.FirstOrDefault() != null)
                // or if (_list.SingleOrDefault() != null)
                // or other IEnumerable<T> method
                {
                    return;
                }
            }
        }
    }
}