Filtering Heterogeneous Arrays in .NET

One of the bugs I was recently asked to fix for an application required me to determine whether or not to display one of the members of a list.  This proved somewhat challenging since the lists in question were heterogeneous (two difference subtypes of an abstract base class).  It turned out that LINQ provides a nice solution to this sort of problem in the form of the OfType<T> method.

Given an IEnumerable collection with elements of multiple types, calling OfType<T> on the collection where T is the desired type will return a collection containing only elements of type T.  Before learning about OfType<T>, I’d been using the Cast<T> method.  This was fine as long as all the collection elements were of the type T I wanted.  The moment this wasn’t the case, my LINQ query threw a cast exception.  OfType<T> seems to work similarly to the “as” operator in C#, in that it doesn’t complain if a list element isn’t type T–it simply excludes it from the returned collection.

PowerGUI and .NET Framework 4.0

On my current project, we use PowerShell scripts to automate our UI testing.  We’ve been writing and running the scripts in the PowerGUI Script Editor, an excellent tool that’s also free.  When we upgraded our application to run on version 4.0 of the .NET Framework from 3.5, we lost the ability to run PowerShell scripts in debug mode from PowerGUI.

The only work-around for this I’ve found (at least until a version of PowerGUI built on .NET 4.0 comes out), is a registry hack that forces all the .NET apps on the machine to use the latest version of the CLR.  You can find more details in this user discussion at, or this discussion on