Style for a derived class is applied in "Design view" but not at runtime

* .NET framework 4.7.2

* Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)? If yes, please file the issue via the instructions [here](https://docs.microsoft.com/visualstudio/ide/how-to-report-a-problem-with-visual-studio?view=vs-2019).

I don't think so; it seems like it works correctly in the designer but not at runtime.

**Problem description:**

As described here: https://stackoverflow.com/q/4279773/3195477 and I have just run into this problem myself.

> It appears that the style for the window is applied when I view the window in the IDE's "Design view" but when I run the application the style is not applied.

Specifically, it seems like a style targeted to a base type will be applied to a derived type in the designer, but not at runtime.

**Expected behavior:** ideally the style would work at runtime, but minimally it would be an improvement for the designer behavior to be consistent and also for an error or warning to be shown.

**Minimal repro:** included in the SO post above.