C#

Performance of algorithms is important topic if you want to write programs that work fast and doesn’t eat too much resources. In this example I will show you two implementations of famous Fibonacci numbers algorithm and let you compare how these two implementations perform. This posting will be also introduction to my next posting to keep it smaller and to keep focus on point.

.Net Framework 4.0 has parallel computing extensions for LINQ. Previously it was possible to download parallel extensions for LINQ separately from CodePlex. Of course, you can still use these extensions if you have older version that 4.0. I wrote a little, simple and pretty pointless example that illustrates how parallel queries work in .Net Framework 4.0.

.Net Framework 4.0 introduced a new class called Lazy. Lazy provides support for several common patterns of lazy initialization, including the ability to initialize value types and to use null values. It’s a powerful and very useful beast but underrated in practice. Here’s how to use it.

ASP.NET provides us with System.Drawing namespace where we can find classes we can use to manipulate with images. There are many people out there who mistakenly think thatImage.GetThumbnailImage is best choice for image resizing. You can easily create crappy images if you follow the code examples in previously pointed article. In this post I will show you how to resize images without negative side effects.

Loggers are one of most popular examples about interfaces for sure. And there are a lot of implementations of loggers. Some implementations are simple and yet powerful, some implementations may be more complex. All we have to is to select implementation we need and integrate it to our application. It seems like good idea at first place but as soon as we need to switch from one implementation to another we discover nasty dependencies we have to change in all places where we are logging. Let’s see how to avoid these dependencies.

I’m sure you have seen classes that initialize a lot of objects in their constructor. These classes may be hard to test because of those object creations I mentioned. To get around this problem we use Extract and override factory method refactoring so we can extend these classes and override some factory methods.

Sometimes you are not able to use Extract Interface refactoring because interface of parameter may be too large or there may be no interface at all. You just have class to pass in and you are not able to fake it or extend it to get class testable. In this case you have to use Adapt Parameter refactoring to create adapter that is seen through common some common class of interface.

In good code variables are used as short as possible. Often we can see code where variables are defined in wider scope than it is necessary. There are many examples about too wide scopes. One of fuzziest of them is variable that is defined in class scope but it used only by one method and this method uses this variable as local variable. But variable life time can also be reduced in local scope. To achieve this we use refactoring method called reduce variable scope.

Casting to types using keyword as is one powerful features of C#. It allows exceptionless casting of reference types. If cast is not possible then null is returned. Although this is powerful language feature it opens also door to some questionable uses.

In legacy code you may find classes with constructor where some objects are created and initialized. These classes are not easily testable because they depend on other classes and therefore when you unit test these classes they may also throw exceptions of classes they depend on. In these cases we can use parameterize constructor refactoring.