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Posted 7 Oct 2008
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Reducing Code Complexity on Switch-blocks

, 7 Oct 2008
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Using a Dictionary instead of a switch-case construction to reduce complexity and increase testability


A switch-block becomes complex very easily. All code is placed in one method and parts of it are used multiple times. In a lot of cases, a switch-block is based on an enum. Next to that, it's not possible to use a fall-through in C#. The only way to go from case to case is the use of the goto statement, which isn't a good idea when reducing complexity. Although I've written the examples in C#, it wouldn't be hard to apply the principles to other languages.

A Solution

A nice solution to get rid of large switch constructions is the use of a Dictionary<enum,delegate>. This way every element of the enum can be attached to a method. It is possible to call the right method for every enum possible. Because every enum has its own method, it's very easy to use this construction in a testdriven environment. Another nice thing is that it's no problem to call one method from another. Let me explain a little further with an example and some pseudo code. Imagine a program that prepares food. This part contains the recipes.

Let us start with the following enum:

Enum food{

It's not hard to imagine that all of the foods need a specific preparation, but that some actions need to be done for different foods, like peeling an apple or baking in the oven.

To add the preparations to the Dictionary<enum, delegate>, we first need to define a delegate method:

delegate bool Preperation();

Now we need to define the actual preparation methods for every item of the enum, making sure they're declared the same way as the delegate, thus the same parameters and return value. The method returns a boolean when preparation is successful.

In this example, the methods may look something like this:

bool PeelApple()
	// code to remove peel
	return true;
bool BakePie()
	return true;
bool MakeAppleJuice()
	return true;
bool BakePizza()
	return true;

Notice that BakePie() and MakeAppleJuice() both call the method PeelApple(). This is not possible in a switch – case constructor, unless you call the methods from each case.

Now all that's left is to create and initialize the Dictionary.

Dictionary<food, /> FoodPreperation;
FoodPreperation = new Dictionary<food, Preperation>();
FoodPreperation.add(food.Apple, new Preperation(PeelApple));
FoodPreperation.add(food.ApplePie, new Preperation(BakePie));
FoodPreperation.add(food.AppleJuice, new Preperation(MakeAppleJuice));
FoodPreperation.add(food.Pizza, new Preperation(BakePizza));

Calling the methods is done by:

food FoodOfChoice = food.ApplePie;

In the last code snippet, the method that goes with food.ApplePie is executed.


  • 07 Oct 2008 - Initial upload


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Timmy Kokke
Software Developer (Senior) Centric Netherlands B.V.
Netherlands Netherlands
Microsoft MVP Client Dev . Founder of, the Dutch Windows Store apps and Windows Phone apps usergroup. XAML / HTML5 developer. Writer. Composer. Musician.


Awards / Honers
• October 2010,2011,2012,2013: Awarded Microsoft Expression Blend MVP
• June 2009: Second Place in the WinPHP challenge
• February 2009: Runner-up in de Mix09 10k Challenge
• June 2008: Winner of the Microsoft expression development contest at

I started programming around 1992, when my father had bought our first home computer. I used GWBasic at that time. After using QBasic and Pascal for a few years I started to learn C/C++ in 1996. I went to the ICT Academy in 1997 and finnished it in 2002. Until December 2007 I worked as a 3D specialist. Besides modelling I worked on different development projects like a 3D based Scheduler and different simultion tools in C# and Java. Though out the years I've gained much experience with ASP.NET, Silverlight, Windows Phone and WinRT.

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Comments and Discussions

GeneralQuite correct approach! Long switch statements are for loosers. Pin
Sergey Alexandrovich Kryukov11-Jan-10 7:44
memberSergey Alexandrovich Kryukov11-Jan-10 7:44 
I confirm by my experience that this approach is quite correct.
Event though you slightly add to memory footprint, you win performance, not only convenience and supportability.
My 5.
I would advise one improvement: add one more method accepting the delegate argument: something like SetDefaultAction to cover all values not found in the dictionary. Initially, this default action should be null.

Thank you.

Sergey A Kryukov

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