Refactoring, tools, Web

Removing unused UserControls with NDepend


NDepend is an amazing analysis tool for .NET code. It gives you deep insight into your code and let you manage its quality easier. It lets the user execute LINQ queries on code, generates dependency graphs, metric view, check rules and many many more. In this post I’ll show a very simple trick to detect unused user controls that can be removed from our project.

NDepend was recommended by Scott Hanselman, Greg Young and others. I tried it some time ago in my small project but I couldn’t benefit from the tool. After some time I had to do some cleaning in our legacy system. Then I came back to the the tool and I have to admit that I fell in love with it.

Some time ago I wrote about Finding unused private and public methods with Resharper. It is of course very nice way of doing code clean-up but in rather smaller systems. In my case Resharper found around 2.5 thousand issues and it’s not an amount that I could face in one or two iterations.

Some issues are specific to particular parts of the solution. In WebForms project the highest level of abstraction is Page and Control. If the user removes/refactors page and decide to not use some user control it becomes dead source of other dependencies.

In the first iteration I decided to get rid of unused pages with help of google analytics report from the last few month. The next one was about dead user controls. Resharper doesn’t allow us to find unused types deriving from specific base type. Here is the place for NDepend.

In “Queries and Rules” section I run the following query:


As a result I got the list of around 30 user controls. Unfortunately this is just an input for further filtering because it lists controls that are not used in code, but not saying anything about markup. All in all checking this is not that hard, one solution is to go through all of them and check what compiler says or find all occurences of “<%@ Register Src="~/Path/MyUserControl.ascx" TagPrefix="uc" TagName="MyControl" %>” for each *.ascx file.