I needed to remove an extraneous generic parameter from two classes in a 2008 project. One of the classes was BusinessObjectList<TList, TItem>, and TList wasn’t used and it ended up junking up the code throughout the solution. I was tired of looking at it and its bizarre subclasses like EmployeeList : BusinessObjectList<EmployeeList, Employee>.

I will note how it could be useful: if any of the methods on BusinessObjectList were returning the subclassed list as part of a fluent interface. But nothing like this exists. I’m not even a fan of defined list classes. Why should you limit yourself when there are other sequence possibilities? What if I had an array of the particular BusinessObject?  I think extension methods on IEnumerable<BusinessObject> are better and it plays better with LINQ (I don’t have to redefine every LINQ method to make it return the list). These are fluent by their nature anyway since you typically make the method yield out the objects creating an IEnumerable<T>.

But, the hard lists are there, and I believe the cost of removing them is too high at this point in time but it’s something I’ll have my eye on if the opportunity exists. Keeping the code tight by removing the extraneous generic is worth it though considering some other framework issues I will be tackling. The problem is that hundreds of classes inherited from this class and the other, and a manual edit would take forever. This refactoring should be quick.

I checked all of my tools, but none had a “remove generic parameter” refactoring. Would I have to do this by hand? Of course not, I’m a programmer. What tool do we have for matching stuff like a BusinessObjectList<X, Y>? How about RegEx?

I pop up the Find/Replace dialog, and immediately type a regex that should match everything I want to replace. It doesn’t work. Now, I’m not an expert in that sort of thing, but surely I can write something that simple? After a few minutes of trying it out, I start searching and discover Jeff Atwood has already talked about this oddity in Visual Studio.

After learning Visual Studio’s flavor of regex, I finally achieved a somewhat bizarre construct for removing a generic parameter. Find what: BusinessObjectList\<:i,:b{:i}\> and Replace with: BusinessObjectList\<\1\>.

The class everything was inheriting from was BusinessObjectList, so I wrote that in and escaped the < and >. :i marks a C/C++ identifier (which works great with C#!) and :b matches tab or space. I enclosed the second :i with curly braces so I could use it as an identifier in the replace regex with \1.

There may not have been a fancy tool to achieve this, but the results were the same and it didn’t take much time. It certainly beats replacing the code by hand.