LINQ Performance Benchmark

Yesterday I was reading “LINQ To Objects Using C# 4.0” by Troy Magennis and find a good LINQ usage example. I got curious about how the LINQ implementation will perform and thought of writing this article.

The example is related to an entity having 3 fields State, LastName and FirstName. The aim is to Group the objects by state and sort by LastName. For calculating the execution time I am using Stopwatch class in System.Diagnosis namespace.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.IO;

namespace ConsoleApplication2
{
public class Customer
{
public string State { get; set; }
public string LastName { get; set; }
public string FirstName { get; set; }
}

class Program
{
static void Main(string[] args)
{
List<Customer> custList = FillListAndGetList();

Stopwatch sw = new Stopwatch();
sw.Start();
#region C# 2.0 Approach

///Sorting by LastName
custList.Sort(
delegate(Customer c1, Customer c2)
{
if (c1 != null && c2 != null)
return string.Compare(c1.LastName, c2.FirstName);
return 0;
});

///Sort and Groupby State [SortedDictionary]
SortedDictionary<string, List<Customer>>
sortedCust = new SortedDictionary<string, List<Customer>>();

foreach (Customer c in custList)
{
if (!sortedCust.ContainsKey(c.State))
sortedCust.Add(c.State, new List<Customer>());

sortedCust[c.State].Add(c);
}

foreach (KeyValuePair<string, List<Customer>>
pair in sortedCust)
{
Console.WriteLine("State : " + pair.Key);

foreach (Customer c in pair.Value)
Console.WriteLine("Last Name : {0}" +
"FirstName : {1} ", c.LastName,
c.FirstName);
}

#endregion

sw.Stop();
File.WriteAllLines("C20", new string[] { sw.ElapsedTicks.ToString() });

custList = FillListAndGetList();
sw.Reset();
sw.Start();

#region LINQ Approach

var query = from c in custList
orderby c.State, c.LastName
group c by c.State;

foreach (var group in query)
{
Console.WriteLine("State : " + group.Key);

foreach (Customer c in group)
Console.WriteLine("Last Name : {0}" +
"FirstName : {1} ", c.LastName,
c.FirstName);
}

#endregion

sw.Stop();
File.WriteAllLines("C20", new string[] { sw.ElapsedTicks.ToString() });
}

private static List<Customer> FillListAndGetList()
{
List<Customer> custList = new List<Customer>();
for (int i = 0; i < 1000000; i++)
{
Customer c = new Customer();
if (i % 2 == 0)
{
c.State = "State2";
c. FirstName = "FirstName2" + i.ToString();
c.LastName = "LastName2" + i.ToString();
}
else if (i % 3 == 0)
{
c.State = "State3";
c.FirstName = "FirstName3" + i.ToString();
c.LastName = "LastName3" + i.ToString();
}
else if(i % 7 == 0)
{
c.State = "State7";
c.FirstName = "FirstName7" + i.ToString();
c.LastName = "LastName7" + i.ToString();
}
else if (i % 11 == 0)
{
c.State = "State11";
c.FirstName = "FirstName11" + i.ToString();
c.LastName = "LastName11" + i.ToString();
}
else
{
c.State = "OtherState";
c.FirstName = "FirstName" + i.ToString();
c.LastName = "LastName" + i.ToString();
}

custList.Add(c);
}

return custList;
}
}
}

Once I ran the application, I got the following result.
C# 2.0 version : 627373008
LINQ version : 692116906
LINQ version has a slight performance problem, but compared to the chunk of code that has gone in 2.0 I think LINQ is far better.