Sorting a list using Lambda/Linq to objects

Question

I have the name of the "sort by property" in a string. I will need to use Lambda/Linq to sort the list of objects.

Ex:

public class Employee
{
  public string FirstName {set; get;}
  public string LastName {set; get;}
  public DateTime DOB {set; get;}
}


public void Sort(ref List<Employee> list, string sortBy, string sortDirection)
{
  //Example data:
  //sortBy = "FirstName"
  //sortDirection = "ASC" or "DESC"

  if (sortBy == "FirstName")
  {
    list = list.OrderBy(x => x.FirstName).toList();    
  }

}

1. Instead of using a bunch of ifs to check the fieldname (sortBy), is there a cleaner way of doing the sorting
2. Is sort aware of datatype?

Answer 1

This can be done as

list.Sort( (emp1,emp2)=>emp1.FirstName.CompareTo(emp2.FirstName) );

The .NET framework is casting the lambda (emp1,emp2)=>int as a Comparer<Employee>.

This has the advantage of being strongly typed.

If you need the descending/reverse order invert the parameters.

list.Sort( (emp1,emp2)=>emp2.FirstName.CompareTo(emp1.FirstName) );

Answer 2

One thing you could do is change Sort so it makes better use of lambdas.

public enum SortDirection { Ascending, Descending }
public void Sort<TKey>(ref List<Employee> list,
                       Func<Employee, TKey> sorter, SortDirection direction)
{
  if (direction == SortDirection.Ascending)
    list = list.OrderBy(sorter);
  else
    list = list.OrderByDescending(sorter);
}

Now you can specify the field to sort when calling the Sort method.

Sort(ref employees, e => e.DOB, SortDirection.Descending);