using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection.Emit;

namespace CreateInstanceTest
{


    class TestClass
    {
    }


    class ClassFactory<T> where T : new()
    {
        public static T Create()
        {
            return new T();
        }
    }

    class Program
    {

        static void CreateInstances(int instances, Action<string, TimeSpan> report)
        {
            var sw = System.Diagnostics.Stopwatch.StartNew();
            for (int i = 0; i < instances; i++)
            {
                var t = new TestClass();
            }
            sw.Stop();
            report("new TestClass();", sw.Elapsed);

            sw.Reset();
            sw.Start();
            for (int i = 0; i < instances; i++)
            {
                var t = Activator.CreateInstance<TestClass>();
            }
            sw.Stop();
            report("Activator.CreateInstance<TestClass>();", sw.Elapsed);

            sw.Reset();
            sw.Start();
            for (int i = 0; i < instances; i++)
            {
                var t = ClassFactory<TestClass>.Create();
            }
            sw.Stop();
            report("ClassFactory<TestClass>.Create();", sw.Elapsed);

            sw.Reset();
            sw.Start();
            for (int i = 0; i < instances; i++)
            {
                var t = Activator.CreateInstance(typeof(TestClass));
            }
            sw.Stop();
            report("Activator.CreateInstance(typeof(TestClass))", sw.Elapsed);

            sw.Reset();
            sw.Start();
            var ctor = typeof(TestClass).GetConstructor(Type.EmptyTypes);
            for (int i = 0; i < instances; i++)
            {
                var t = ctor.Invoke(null);
            }
            sw.Stop();
            report("ctor.Invoke(null)", sw.Elapsed);

            sw.Reset();
            sw.Start();
            var dynMethod = new DynamicMethod("blabla", typeof(TestClass), Type.EmptyTypes, typeof(TestClass));
            var ilGen = dynMethod.GetILGenerator();
            ilGen.Emit(OpCodes.Newobj, typeof(TestClass).GetConstructor(Type.EmptyTypes));
            ilGen.Emit(OpCodes.Ret);
            var creator = (Func<object>)dynMethod.CreateDelegate(typeof(Func<object>));
            for (int i = 0; i < instances; i++)
            {
                var t = creator();
            }
            sw.Stop();
            report("creator()", sw.Elapsed);

            sw.Reset();
            sw.Start();
            var lambdaCreator = (Func<object>)System.Linq.Expressions.Expression.Lambda(System.Linq.Expressions.Expression.TypeAs(System.Linq.Expressions.Expression.New(typeof(TestClass)), typeof(object))).Compile();
            for (int i = 0; i < instances; i++)
            {
                var t = lambdaCreator();
            }
            sw.Stop();
            report("lambdaCreator()", sw.Elapsed);
        }

        static void Main(string[] args)
        {
            CreateInstances(1024 * 1024, (m, t) => Console.WriteLine("{0}:\t{1} ms", m, t.Ticks / 10000.0));
            //CreateInstances(1024 * 1024, (m, t) => Console.WriteLine("<tr><td><em>{0}</em></td><td>{1}</td><td>1,0</td></tr>", m, t.Ticks / 10000.0));

            Console.Read();
        }
    }
}