Cannot implicitly convert List to Collection

Question

This is a compiler error (slightly changed for readability).

This one always puzzled me. FxCop tells that this is a bad thing to return List and classes that are\\de

Answer 1

This is how you convert from List to Collection (while using LINQ):

The old function:

public List GetEmployee(int id)
{
     return ( from e in MyDataContext.Employees
                   select new Employee()
                   {
                     e.empId = id
                   }
             ).ToList();
}

After conversion:

using System.Collection.ObjectModel;

public Collection GetEmployee(int id)
{
           return new Collection( 
               (from e in MyDataContext.Employees
                     select new Employee()
                     {
                       e.empId = id
                     }
                ).ToList() as IList
           );
}