ExpressionsSample / EntityType (Lambda)

EntityType.cs

using System;
using System.Diagnostics;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace ExpressionsConsole
{
    [DebuggerDisplay(@"{typeof(TEntity)}")]
    public class EntityType<TEntity>
    {
        public ConstructorInfo ConstructorInfo { get; private set; }

        Func<object[], TEntity> _constructor;

        internal EntityType(ConstructorInfo constructorInfo)
        {
            ConstructorInfo = constructorInfo;

            _constructor = CompileConstructor(constructorInfo);
        }

        public TEntity CreateEntity(params object[] parameters)
        {
            return _constructor(parameters);
        }

        static Func<object[], TEntity> CompileConstructor(ConstructorInfo constructorInfo)
        {
            var parameterInfoes = constructorInfo.GetParameters();
            var p = Expression.Parameter(typeof(object[]), "p");
            var ctorExp = Expression.New(constructorInfo, parameterInfoes.Select(i => GetParameterValue(p, i)));

            // p => new TEntity((int)p[0], (string)p[1])
            var ctorLambda = Expression.Lambda<Func<object[], TEntity>>(ctorExp, p);
            return ctorLambda.Compile();
        }

        static Expression GetParameterValue(ParameterExpression p, ParameterInfo info)
        {
            var p_i = Expression.ArrayIndex(p, Expression.Constant(info.Position));
            return Expression.Convert(p_i, info.ParameterType);
        }
    }
}

Program.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ExpressionsConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            EntityTypeTimeTest();
        }

        static void EntityTypeTimeTest()
        {
            var sw = Stopwatch.StartNew();

            var PersonType = EntityType.Create(new { Id = 0, Name = "", Birthday = DateTime.MinValue });

            Console.WriteLine(sw.Elapsed);

            for (var i = 0; i < 1000000; i++)
                PersonType.CreateEntity(i, "Person", DateTime.MaxValue);

            sw.Stop();
            Console.WriteLine(sw.Elapsed);
        }
    }
}