Question

I have a class definition that looks like this:

public class MyObjectModel
{
   public int ObjectID { get; set; }

   //for when the user's data is split in 2 fields
   public string FirstName { get; set; }
   public string LastName { get; set; }

   //for when the user's data is all in one field
   public string FirstLastName { get; set; }
}

I have a list of these MyObjectModel and I want to sort them by name with a custom sort process because that involves checking if the data contains a LastName (in this case sort using the LastName) or just FirstLastName (in this case I’m going to break the string and sort on the second term, if there’s one, or just the whole string if there’s only one word.)

I’m not sure on two things:

1. should I use IComparer or IComparable?
2. Once it determines the order of the sort (I can do that), how do I make it so that the output of the method is a list of ints representing ObjectID.

Answer 1

Use Linq:

  List<MyObjectModel> objects = new List<MyObjectModel>();
  List<int> ids = objects.OrderBy(o => FunctionWhichReturnsNameForSort(o)).Select(o => o.ObjectID).ToList();

FunctionWhichReturnsNameForSort can be implemented in another class, or an extension, or as a member.

// should be in a static helper class
public static string NameForSort(this MyObjectModel obj)
{
  if (!string.IsNullOrEmpty(obj.LastName)) return obj.LastName;

  return obj.FirstLastName.Split(... // your splitting logic goes here
}

var ids = objects.OrderBy(o => o.NameForSort()).Select(o => o.ObjectID).ToList();