Extension method to lazy loading related fields of an entity

EFLazyLoadingExtensions.cs

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

namespace CodeZone.EntityFramework.Extensions
{
    public static class EFLazyLoadingExtensions
    {
        public static void Load<TEntity, TRelated>(this TEntity entity, Expression<Func<TEntity, TRelated>> relatedSelector)
            where TRelated : class
        {
            var lazyLoaderInfo = entity.GetType().GetField("_lazyLoader", BindingFlags.Instance | BindingFlags.NonPublic);
            if (lazyLoaderInfo == null) throw new InvalidOperationException("Entity must declare a private field '_lazyLoader' of type 'Action<object, string>' injected by constructor.");

            var lazyLoader = lazyLoaderInfo.GetValue(entity) as Action<object, string>;
            var relatedProperty = (relatedSelector.Body as MemberExpression).Member;

            lazyLoader.Invoke(entity, relatedProperty.Name);
        }
    }
}