Friday, December 28, 2007
Twelve Days of Refactor! X-mas, Day Nine: Expand Lambda Expression

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Welcome back for more X-mas refactoring fun! There are just four more verses in my carol, but I'll make them count. Refactor! Pro can bless your Visual Studio 2008 installation in many more ways, so I'll have to pick the very best.

"On the ninth day of X-mas my true love (DevExpress) gave to me..."

Expand Lambda Expression

In my sixth verse, I described a feature of Refactor! Pro that enables developers to leverage the dreaded lambda expressions. That refactoring (Compress to Lambda Expression) provides a way to transform an anonymous method into a lambda expression. Today we're looking at lambda expressions from the opposite perspective—transforming a lambda expression into an anonymous method. Expand Lambda Expression is the refactoring that performs this conversion. Given the lambda expression in the code below...

using System;

namespace TwelveDaysOfXmas
{
  class Program
  {
    static void Main()
    {
      var numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

      var numberText = Array.ConvertAll<int, string>(numbers, n => n.ToString("x8"));

      foreach (var text in numberText)
        Console.WriteLine(text);
    }
  }
}

Expand Lambda Expression will produce this:

using System;

namespace TwelveDaysOfXmas
{
  class Program
  {
    static void Main()
    {
      var numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

      var numberText = Array.ConvertAll<int, string>(numbers, delegate(int n)
                                                              {
                                                                return n.ToString("x8");
                                                              });

      foreach (var text in numberText)
        Console.WriteLine(text);
    }
  }
}

I'm sure that some of you are scratching your heads. "Why in the world would I want to do that? Aren't lambda expressions better?" Well, yes. However, transforming a lambda expression into an anonymous method makes other refactorings available. For example, after expanding our lambda expression, we might want to use Name Anonymous Method to make the anonymous method a member of the current type. That way, we're promoting code reuse. Check out the preview hint for Name Anonymous Method below.

Name Anonymous Method Preview Hint

Once Name Anonymous Method is applied, we can give the new method a good name and we're done!

using System;

namespace TwelveDaysOfXmas
{
  class Program
  {
    private static string GetHexText(int n)
    {
      return n.ToString("x8");
    }
    static void Main()
    {
      var numbers = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

      var numberText = Array.ConvertAll<int, string>(numbers, GetHexText);

      foreach (var text in numberText)
        Console.WriteLine(text);
    }
  }
}

View Screencast of Expand Lambda Expression and Name Anonymous Method in Action!

I must say, it gladdens my heart to know that there is a tool available right now that allows me to refactor the latest and greatest language features of Visual Studio 2008. In fact, we've raised the bar by releasing a major update to Refactor! Pro. That's right, Refactor! Pro 3.0 is now available and ships with 150 refactorings for C#, Visual Basic, C++, ASP .NET, XAML, and even JavaScript. The future is looking very bright indeed!

12 Days of Refactor! | C# | Quality Code | Refactor! | Visual Studio
posted on Friday, December 28, 2007 12:53:10 PM (Pacific Standard Time, UTC-08:00)  #    Comments [0]

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Related posts:
Empty Nothings
Naming Anonymous Types with Generate from Usage
Lesser-Known VB: Customizing the Completion List
YAPES: Problem Seven, Part 2
YAPES: Problem Seven, Part 1
YAPES: Problem Six
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