This works when you don't use ThenBy
-type operations (which are all the IOrderedEnumerable<T>
interface really adds). See C#: How to implement IOrderedEnumerable<T> for a solution to support that.
public class Employee
{
public string Name {get;set;}
public int employee_id {get;set;}
public int Age {get;set;}
}
public class EmployeeCollection : IEnumerable, IEnumerable<Employee>, IOrderedEnumerable<Employee>
{
public Func<Employee, object> SortOrder {get;set;}
public Func<Employee, bool> Filter {get;set;}
protected Dictionary<int,Employee> EmployeeById = new Dictionary<int,Employee>();
public void Add(Employee ePassed)
{
EmployeeById[ePassed.employee_id] = ePassed;
}
public IEnumerator<Employee> GetEnumerator()
{
var employees = EmployeeById.Keys.Select(id => this.GetEmployee(id));
if (Filter != null)
employees = employees.Where(Filter);
if (SortOrder != null)
employees = employees.OrderBy(SortOrder);
return employees.GetEnumerator();
}
public Employee GetEmployee(int id)
{
return EmployeeById[id];
}
IEnumerator IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
public IOrderedEnumerable<Employee> CreateOrderedEnumerable<TKey>(Func<Employee, TKey> KeySelector, IComparer<TKey> comparer, bool descending)
{
throw new NotImplementedException();
}
}
// this is some code you might use to test this:
var EmployeeCollection = new EmployeeCollection
{
new Employee { employee_id = 1, Age = 20, Name = "Joe" },
new Employee { employee_id = 2, Age = 30, Name = "Thomas" },
new Employee { employee_id = 3, Age = 25, Name = "Robert" },
};
EmployeeCollection.SortOrder = x => x.Age;
EmployeeCollection.Filter = x => x.Name.Length > 4;
foreach (Employee e in EmployeeCollection)
{
// do something
}