如何将Entity类解析为具有Extension的自定义Entity类

我想编写一个自定义类扩展。我有EDMX类，但我想解析为CUSTOM类。例如，Customer类有3个属性（id、name、surface），而我的自定义Customer类则有3个特性（id、name。我想使用扩展名将List<Customer>解析为List<MyCustomer>，但如何做到这一点？

public partial class MyVisitorAdvertisement
{
    public int ID { get; set;}
    public int VID { get; set;}
    public int TID { get; set;}
    public string Detail{ get; set;}
    public DateTime Date { get; set;}
    public DateTime LastDate { get; set;}
    public MyVisitorAdvertisement()
    {
    //constructor
    }
    public List<MyVisitorAdvertisement> ListByID( int ID)
{
    List<MyVisitorAdvertisement> visitors = new List<MyVisitorAdvertisement>();
    using (var Ctx = new DomainRepository<VisitorAdvertisement>(new ProposalsEntities()))
    {
        foreach (var visitor in Ctx.Find<VisitorAdvertisement>(q => q.ID == ID).ToList())
        {
            MyVisitorAdvertisement visitoradvertisement = new MyVisitorAdvertisement();
            visitoradvertisement.ID = visitor.ID;
            // i dislike to do it. i think that how to make it a extention?    
            visitors.Add(visitoradvertisement);
        }
        return visitors;
    }
}
}

我想要的分机：

public static List<TResult> (this IEnumerable<T> mylist) where TResult,T: class
{
  return //mylist parse to List<TResult>
}

public static List<TResult> ListByID<TResult>(this IEnumerable<T> mylist) where TResult : VisitorAdvertisement where T: class
{
   return Ctx.Find<TResult>(q => q.ID == ID).SelectMany(a => new TResult{ Id = a.Id}).ToList();
}