记事本

namespace System.Extension.Dynamic
{
    public static class Dynamic
    {
        private static Dictionary<PropertyInfo, object> propertyGetters = new Dictionary<PropertyInfo, object>();
        public static object Property(this object instance, string name)
        {
            var instanceType = instance.GetType();
            var propertyInfo = instanceType.GetProperty(name);
            if (propertyInfo == null) throw new InvalidOperationException();
            if (!propertyInfo.CanRead) throw new InvalidOperationException();

            object compiled;
            if (!propertyGetters.TryGetValue(propertyInfo, out compiled))
            {
                var parameter = Expression.Parameter(typeof(object), "obj");
                var convertParameter = Expression.Convert(parameter, instance.GetType());
                var property = Expression.Property(convertParameter, propertyInfo);
                var convertReturnValue = Expression.Convert(property, typeof(object));
                var lambda = Expression.Lambda(convertReturnValue, parameter);
                compiled = lambda.Compile();
                propertyGetters.Add(propertyInfo, compiled);
            }
            return ((Func<object, object>)compiled)(instance);
        }
    }
}