How about this association ORM

public class Employee
{
    public byte ID { get; set; }
    public string Name { get; set; }
}
public class Task 
{
    public int ID { get; set; }
    public string Description { get; set; }


    private  List<Employee> employeeTask ;
    public  List<Employee> EmployeeTask
    {
            get
            {
                if (employeeTask == null)
                {
                    employeeTask = //Any Source changeable ;
                }
                return employeeTask; 
            }
    }
}
class Program
{
    void main()
    {
         List<Task> ListTask = //fill with groub of Tasks;
                               /*When Call 
                               property EmployeeTask in every Object in list (ListTask), 
                               the property(EmployeeTask) in all Object 
                               have the Same content (have last content element)*/
     }
}