Entity Framweork: How to set model as Serializable in entity framework

Entity Framweork: How to set model as Serializable in entity framework

using System;
using System.Collections.Generic;
[Serializable]
public partial class user
{
public int UserId { get; set; }
public string Name { get; set; }
public string Surname { get; set; }
public string UserName { get; set; }
public string Email { get; set; }
public string Password { get; set; }
public System.DateTime Creation { get; set; }
public bool Status { get; set; }
public int UserTypeId { get; set; }
}
As you can see in my code, my class setted as serializable. But after I
update my .edmx file, this setting deleted. How can I keep Serializable
after update edmx file?