Dot Net Perls

Problem

Sort strings by length (shortest string first and longest string last, or the opposite) in .NET 3.5. This is not a hot or critical part of our code, so it doesn't need to be super fast, but it should be relatively fast and not create a problem. Let's look at some sample output first.

Solution: C#

As I noted, there are many ways to solve this problem. The solution here requires LINQ, which is included in .NET 3.5. Let's take a peek at the code, and I will review it afterwards. The first example block on this page uses string arrays, and the one near the end of this post uses the List.

class TestClass
{
    public TestClass()
    {
        //
        // Initialize a list of strings.
        //
        List<string> sampleList = new List<string>
        {
            "stegosaurus",
            "pirahna",
            "leopard",
            "cat",
            "bear",
            "hyena"
        };
        //
        // Send a string array to the method.
        //
        SortByLength(sampleList.ToArray());
    }

    private static string[] SortByLength(string[] arrayIn)
    {
        //
        // Use LINQ to sort the array received and return a copy.
        //
        var sorted = from oneString in arrayIn
                     orderby oneString.Length ascending
                     select oneString;
        return sorted.ToArray();
    }
}

• SortByLength is static
  This method is static because it doesn't need to save state
• Code above uses string arrays
  SortByLength receives a string[] array. Later in this page there is an example with List.
• LINQ var keyword is used
  A variable is created from the LINQ statement that uses select, from, orderby and ascending. The IEnumerable var is returned as an array.

LINQ Syntax

The syntax in the var statement are functional programming but are equivalent to writing the code out long-hand. My example uses this syntax because I feel it is easily the clearest to understand. I strongly suggest learning and using LINQ as offers a whole new level of programming ease.

List Version

Many C# programmers use generics like List<string> more often, and even though they are a tiny bit slower, they work very well. Here is a version of the above function that uses generic List objects. You can put it side-by-side with the other SortByLength function, and the compiler will choose the best one for your code (method overloading).

/// <summary>
/// Sort list generics and return a copy of the List.
/// </summary>
/// <param name="listIn">The List you want to sort.</param>
/// <returns>The new sorted List.</returns>
private static List<string> SortByLength(List<string> listIn)
{
    var sorted = from oneString in listIn
                 orderby oneString.Length ascending
                 select oneString;
    return sorted.ToList();
}

Discussion

Sort your strings using LINQ for a method that is fairly fast, easy to read, and quick to type. Don't bother implementing IComparable or doing anything else complicated. Just type it out in LINQ using select, orderby, and ascending keywords. Finally, you can use any property on objects as the sorting key, not just Length.

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