In this post I will show you how to perform dynamic sorting with LINQ. I will work with a simple collection of City class. City class is defined below.

public class City

{

    public string Name { get; set; }

    public string Country { get; set; }

}

The collection is initialised using this code

List<City> cities =

            new List<City>

            {

                new City{ Name = "Sydney", Country = "Australia" },

                new City{ Name = "New York", Country = "USA" },

                new City{ Name = "Paris", Country = "France" },

                new City{ Name = "Milan", Country = "Spain" },

                new City{ Name = "Melbourne", Country = "Australia" },

                new City{ Name = "Auckland", Country = "New Zealand" },

                new City{ Name = "Tokyo", Country = "Japan" },

                new City{ Name = "New Delhi", Country = "India" },

                new City{ Name = "Hobart", Country = "Australia" }

            };

A typical example of applying a sort will be to write such a query.

var collection =

    from c in cities

    orderby c.Country

    select c;

Here we are sorting the collection on country. Note that this is static in nature.

Code above as you can see can only sort by country. If I wanted to sort by city name then I’d be writing another query and maybe use a conditional construct such as if or switch and write a method which takes in a parameter. While this will work, it is not the best way to do it.

LINQ gives us the ability to make our code dynamic. I can provide sort functionality for my query by writing a method which takes in a Func<TElement, TKey> delegate. This delegate is used by the OrderBy extension method. This is how I can write my method.

public static void Sort<TKey>(List<City> cities, Func<City, TKey> selector)

{

    var sortedCollection =

        from c in cities

        orderby selector(c)

        select c;

    foreach (var item in sortedCollection)

    {

        Console.WriteLine(item.Name);

    }

}

This method can be called like this by passing in the cities collection which has been initialised earlier.

Sort(cities, c => c.Name);

I can also sort by country without changing my query. To sort by country I just need to call my sort method like this.

Sort(cities, c => c.Country);

LINQ is very powerful when you start using it on daily bases. It would not be very useful if everything was static. In this post I showed you how you can make your sorting code dynamic. Stay tuned for more LINQ goodness.