Twelve Days of Refactor! X-mas, Day One: Make Implicit : CSharp Feeds

Twelve Days of Refactor! X-mas, Day One: Make Implicit

by Dustin Campbell via Did it with .NET on 12/20/2007 6:31:39 PM

Fireplace

Gentle readers, in the spirit of X-mas, I'd like to sing you a carol. This jolly tune (based on a popular old English carol) enumerates ways that Refactor! Pro can warm your installation of Visual Studio 2008 this holiday season. In contrast to some of our... ahem... <whisper>competition</whisper>, the features I'll be showing can be used today. In fact, most of these features have been shipping since Visual Studio 2008 was still a wee child known by its code name, Orcas.

But, hey, enough of my yammering! Stoke the fire and put on a kettle! Let the merry-making begin!

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

Make Implicit

Visual Studio 2008 introduced a welcome addition to both the C# and Visual Basic languages: implicitly-typed local variables. While this feature is necessary to properly support another feature, anonymous types, it can also be used to enhance the readability of client code—especially when generic types are being used. Consider the following code:

          private

          static

          Dictionary<string, Guid>

BuildIdTable()

{

  Dictionary<string, Guid>

map = new Dictionary<string, Guid>();

  // Fill map with entries...

  return map;

}

That sort of code can be a bit frustrating. Dictionary<TKey, TValue> is extremely powerful, but can be awkward to use. The developer is forced to fully declare the type name (which is often quite long) on both the left and right sides of the local variable declaration. Thankfully, an implicitly-typed local variable can alleviate this problem:

          private

          static

          Dictionary<string, Guid>

BuildIdTable()

{

  var map = new Dictionary<string, Guid>();

  // Fill map with entries...

  return map;

}

Now for the really good news: Refactor! Pro provides Make Implicit, a refactoring which easily converts explicitly-declared local variables to implicit ones. Check out the preview hint for Make Implicit:

View Screencast of Make Implicit in Action!

Of course, like most of our refactorings, Make Implicit works in Visual Basic as well.

Some critics might be thinking, "What's the point? It just deletes text and inserts a keyword! I could write a macro to do that!" Well, before those skeptics get too comfortable with their new macro, consider what Make Implicit must do with code like the following:

          ulong number = 42;

If Make Implicit were simply to swap ulong for var, there would be a serious problem. Instead of ulong, the type of number would be inferred as int, changing the meaning of the code. To fix this problem, a minor adjustment is made to prevent shooting the code in its proverbial foot.

          var number = 42ul;

So, throw your macro away! Let Make Implicit handle the edge cases intelligently.

Ho, ho, ho! That's quite a gift under the tree! Come back tomorrow when I continue my jaunty tune and look at another Visual Studio 2008-specific refactoring that is available to you today:Make Explicit.