using System;
using System.Reflection; 

namespace AttributeExample
{
   class Program
   {
      static void Main(string[] args)
      {
         MyProperties bag = new MyProperties();

         foreach (PropertyInfo pi in typeof(MyProperties).GetProperties())
            if (IsLightweight(pi.Name)) Console.WriteLine(pi.Name);
         
         Console.ReadLine(); 
      }

      static bool IsLightweight(string prop)
      {
         if (typeof(MyProperties).GetProperty(prop).GetCustomAttributes(typeof(LightweightAttribute), true).Length > 0)
            return true;
         return false;
      }

   }

   public class LightweightAttribute : Attribute
   {
      public LightweightAttribute() { }
   }
   
   public class MyProperties
   {
      public int Size { get; set; }

      [Lightweight()]
      public string LastName { get; set; }

      [Lightweight()]
      public string FirstName { get; set; }
   }
}