.NETpad 2025: .NET 9.0.1 Fixes the App Crashing Bug (Premium)

I wasn’t expecting to publish a .NETpad 3.0 update this quickly, at least not on this topic, but Microsoft released .NET 9.0.1 today. And as I had hoped–and assumed–it includes the hoped-for fix for the bug that caused the app to crash when the user expanded an Expander control and then changed the app theme. So I’ve updated the project by removing the temporary App theme button I had previously added and updating the code-behind accordingly.

So this will be a quick update.

I saw the post .NET and .NET Framework January 2025 servicing releases updates in my news feed this morning and perked up immediately. As you may know, I’ve been waiting for this update. Well, assuming it included the fix for that bug Microsoft introduced into Windows Presentation Foundation (WPF), its new support for Windows 11 theming, and .NET 9. Finding any reference to the fix proved tedious–the release notes don’t mention this at all–so I gave up after a while and just installed the update. Then I opened .NETpad in Visual Studio, ran the app, used an Expander control, and changed the theme. It works. No more crashing.

In doing that, I was alerted to a minor update to Visual Studio 2022 as well, which updates from version 17.12.3 to 17.12.4. Obviously, this is nothing major–it’s described as a cumulative update with new features, updated components, and servicing fixes–but it also wasn’t required to use .NET 9.0.1. But I’m installing that now as well.

Anyway, this is a minor change to the app that involved:

• Removing the app theme button (really a menu bar item) and its sub-menu items from the main app window.
• Removing references to those controls from the code

And that’s it. I updated the project repository on GitHub so you will get the latest version with this change if you download it going forward. Note that you will need to install .NET 9.0.1 or the app will crash if you change the theme after having expanded an Expander control. But with 9.0.1, it works as expected.

Beyond this, I’ve been working on updating the app in ways both big and small. In addition to the settings auto-flow change, that’s not yet up in GitHub, I’ve also created custom Message Boxes for those few times the app displays one. I’ve spent a lot of time working on session state, which is a major feature, though I’ve made some good progress there. And I just started using GitHub Copilot, which integrates with Visual Studio and has a free tier, to do some code improvement passes. I will be writing about all these updates soon and will continue pushing the changes to GitHub as I go.

More soon.