Using SortedSet as a Sorted List with Custom Comparer – c#

chrisbitting, , , ,

Sometimes you have a list of objects you want to stay sorted. You can usually use an IList and then linq: orderby to sort the list – but other times it helps to have the list always sorted. In those times, SortedSet works very well. In my below example, a sorted set contains some people – and whenever you look at the list in the SortedSet – they are already sorted (by age, name & location).

I was concerned about the performance of the SortedSet vs. a List, so after running some tests, as expected – the SortedSet needs some initial time when adding items (to compare) vs. the List which will is fast to write to – but needs a little time when sorting the list after. Below is some really fast numbers (data in milliseconds) I’ve compiled based on adding / reading 25000 records:

sortedSet-performance

Below is the sample using SortedSet and an IComparer:

using System;
using System.Collections.Generic;

namespace sortedSet
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            //create the SortedSet
            SortedSet<Person> people = new SortedSet<Person>(new PersonComparer());

            //add some random folks:
            Random rnd = new Random();
            for (int i = 1; i <= 25; i++)
            {
                //new person
                Person person = new Person();
                person.name = "Bob " + i.ToString();
                person.location = "Miami" + i.ToString();

                //random age
                int r = rnd.Next(1, 99);
                person.age = r;

                //add person to set
                people.Add(person);
            }

            //show our list:
            foreach (Person person in people)
            {
                Console.WriteLine(person.name + " - Age: " + person.age.ToString());
            }

            Console.ReadLine();
        }
    }

    //create comparer
    internal class PersonComparer : IComparer<Person>
    {
        public int Compare(Person x, Person y)
        {
            //first by age
            int result = x.age.CompareTo(y.age);

            //then name
            if (result == 0)
                result = x.name.CompareTo(y.name);

            //a third sort
            if (result == 0)
                result = x.location.CompareTo(y.location);

            return result;
        }
    }

    internal class Person
    {
        public string name { get; set; }

        public string location { get; set; }

        public int age { get; set; }
    }
}

-If you don’t have a need to sort your lists – don’t forget about HashSet (very fast).

Using SortedSet as a Sorted List with Custom Comparer – c#

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