Update TypeTestingAndConversionOperators.cs

[Xamarin2019]

Fixed code snippet for array casting example.

Now it works in browser.

Summary

Checking the code in the browser raised an error.

I'm happy to help Microsoft!

[Xamarin2019]

Dear team!
I think you need unit tests for code samples.

[BillWagner]

closing and reopening for a fresh CI build.

[BillWagner]

Thanks @Xamarin2019

This LGTM, and I'll as soon as the build finishes.

[BillWagner]

Dear team! I think you need unit tests for code samples.

We know. It's a harder problem than it appears at first.

Most importantly, we don't want the introduction of unit tests to make the reader's experience worse. For example, it's easy to copy / paste / modify samples that use Console.WriteLine to experiment with an API or a concept. Those are hard to unit test, and brittle when you do. We're working on some technology that would enable us to "replay" the steps for code in an article and verify the results. Those show promise, but aren't perfect yet.

In the meantime, we have a CI system to (at least) catch compiler errors.