List<T>の内部の配列を取得するやつ（with Static Type Cache）

ListUtil.cs

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


namespace Koturn
{
    /// <summary>
    /// Provides some utility methods of <see cref="List{T}"/>.
    /// </summary>
    public static class ListUtil
    {
        /// <summary>
        /// Get internal array of <see cref="List{T}"/>.
        /// </summary>
        public static T[] GetArray<T>(List<T> list)
        {
            return ListUtil<T>.GetArray(list);
        }
    }

    /// <summary>
    /// Provides some utility methods of <see cref="List{T}"/>.
    /// </summary>
    public static class ListUtil<T>
    {
        /// <summary>
        /// Cache of delegate of <see cref="CreateGetArrayFunc"/>.
        /// </summary>
        private static Func<List<T>, T[]> _getArray;

        /// <summary>
        /// Get internal array of <see cref="List{T}"/>.
        /// </summary>
        /// <param name="list">Target list.</param>
        /// <returns>Internal array of <see cref="List{T}"/>.</returns>
        public static T[] GetArray(List<T> list)
        {
            if (_getArray == null)
            {
                _getArray = CreateGetArrayFunc();
            }
            return _getArray(list);
        }

        /// <summary>
        /// Create method which gets internal array of <see cref="List{T}"/>.
        /// </summary>
        /// <typeparam name="T">Element type of <see cref="List{T}"/>.</typeparam>
        private static Func<List<T>, T[]> CreateGetArrayFunc()
        {
            var dynMethod = new DynamicMethod(
                "GetListArray",
                typeof(T[]),
                new [] { typeof(List<T>) },
                true);

            var ilGen = dynMethod.GetILGenerator();
            ilGen.Emit(OpCodes.Ldarg_0);
            ilGen.Emit(
                OpCodes.Ldfld,
                typeof(List<T>).GetField(
                    "_items",
                    BindingFlags.GetField
                        | BindingFlags.NonPublic
                        | BindingFlags.Instance));
            ilGen.Emit(OpCodes.Ret);

            return (Func<List<T>, T[]>)dynMethod.CreateDelegate(typeof(Func<List<T>, T[]>));
        }
}