C# extension methods are a great idea but they do suck goat balls (I know the term is donkey balls, but goat balls are bigger) when you're trying to look up the source of something. In order to do that you first have to figure out which assembly contains the method (https://packagesearch.azurewebsites.net/ helps a lot) and then have to find the source tree that contains that method, which isn't always trivial since e.g. asp.net core is spread out over like 10 repos.