AvaloniaVS Won't Install On VS 2026? Here's Why!

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Hey guys! If you're trying to get AvaloniaVS up and running in Visual Studio 2026 Insiders and hitting a wall, you're not alone. Based on the details provided, it seems like there's a compatibility issue preventing the extension from installing correctly. Let's break down the problem and see what we can do. We'll cover the reported bug, the steps to reproduce it, and the potential solutions, all while keeping it friendly and easy to understand.

The Problem: AvaloniaVS and VS 2026 Insiders

The core issue, as described by the user, is that the AvaloniaVS plugin (specifically version 11.9) fails to install in Visual Studio 2026 Insiders. The error message Object reference not set to an instance of an object. suggests that something within the installation process is not able to find or access the necessary components.

This error often pops up when there's a mismatch between the extension and the Visual Studio version, or when required dependencies aren't met. Given that VS 2026 Insiders is a preview version, it's quite possible that the AvaloniaVS plugin hasn't been fully updated to support the latest changes in the IDE. Let's dive into what might be causing this, and how you can possibly fix it.

Understanding the Error

The error message "Object reference not set to an instance of an object" is a common one in .NET development. It basically means that a piece of code is trying to use an object that hasn't been properly initialized or doesn't exist. In the context of a Visual Studio extension installation, this can happen for several reasons. These are some of the possible causes, but not limited to them:

  • Compatibility Issues: The AvaloniaVS extension might not be fully compatible with the specific version of Visual Studio 2026 Insiders you're using. Preview versions of VS often have breaking changes. This incompatibility prevents the extension from correctly accessing the required Visual Studio components.
  • Dependency Problems: The extension may depend on certain .NET libraries or Visual Studio SDK components that are either missing or not correctly configured in your Insiders installation.
  • Installation Corruption: There could be an issue with the VSIX installer itself, or with the way the extension files are structured, preventing them from being correctly unpacked and loaded.

Steps to Reproduce the Issue

The user provided a clear way to reproduce the problem, which is super helpful in getting to the bottom of it.

  1. Download the VSIX: Grab the AvaloniaVS.VS2022.vsix file from the Visual Studio Marketplace. Keep in mind that the file is for Visual Studio 2022.
  2. Run the VSIX Installer: Use the VSIX Installer to install the downloaded file.
  3. Encounter the Error: The installation process throws the error Object reference not set to an instance of an object. This means that the plugin couldn't install and will not be available for you to use.

Analyzing the Log Output

The provided log output gives us a good look into what is happening during the installation. Here are some key observations:

  • Visual Studio Version: The log confirms that the user is indeed using Visual Studio 2026 Insiders (version 18.0.0). This is crucial because Insiders builds can have significant changes compared to the stable releases.
  • VSIX Installer Version: The VSIX Installer version is also important. It's good to know that the user is using a compatible installer.
  • Skipped Products: The installer skips the BuildTools product. This is normal, as the extension is not designed for BuildTools.
  • Product Detection: The installer successfully identifies the installed Visual Studio Community 2026 Insiders.
  • Extension Details: The log provides details about the AvaloniaVS extension, including its name, author, version, and supported Visual Studio versions.
  • Supported Versions: The log shows that AvaloniaVS supports Visual Studio versions from 17.0 up to 18.0. This might be the problem. Because the Visual Studio version is higher than 18.0, the extension might be having some compatibility issues.
  • Signature State: The extension is unsigned. Unsigned extensions can sometimes have installation problems, although this isn't always the case.
  • Error Message: The main error message, Object reference not set to an instance of an object., is the key clue. It means that the installer encountered a problem when trying to initialize or access certain objects.

Potential Solutions and Workarounds

Okay, so what can we do to try and fix this? Here are a few things you can try, keeping in mind that since this is an Insiders build, some solutions might be temporary:

1. Check for AvaloniaVS Updates

  • Look for Beta or Preview Versions: Check the Visual Studio Marketplace or the Avalonia project's website for a beta or preview version of the AvaloniaVS extension that specifically targets Visual Studio 2026. This version might have the necessary compatibility fixes.
  • Contact the Developers: Reach out to the Avalonia team to ask if they're aware of the issue and if they have a timeline for a fix.

2. Ensure .NET SDK Compatibility

  • Verify .NET SDK Version: Make sure you have a compatible .NET SDK installed. Some extensions rely on specific .NET versions. Check the AvaloniaVS documentation to see which .NET versions are supported.
  • Update .NET: Update your .NET SDK to the latest version to ensure that you have the necessary libraries and tools.

3. Manual Installation (Advanced)

  • Extract the VSIX: Try extracting the contents of the AvaloniaVS.VS2022.vsix file. You can do this by renaming the file to .zip and then extracting it.
  • Manually Copy Files: Sometimes, you can manually copy the extension files to the Visual Studio extensions directory. The location will be something like C:\Users\<YourUsername>\AppData\Local\Microsoft\VisualStudio\18.0_xxxxxxxx\Extensions. Be careful with this, as incorrect placement can cause problems.
  • Use with Caution: Manual installation is not recommended, and it may not work. It's best to wait for an updated extension version.

4. Check Visual Studio Installation

  • Repair Visual Studio: In the Visual Studio Installer, try the "Repair" option for your Visual Studio 2026 Insiders installation. This can fix any corrupted files that might be causing the issue.
  • Update Visual Studio: Make sure your Visual Studio 2026 Insiders installation is fully updated. Sometimes, even preview versions need updates to fix bugs and improve compatibility.

5. Investigate the Error in Detail

  • Examine the Log: The log output shows the exception. If you can get a more detailed log (e.g., by running the installer from the command line), it may offer more insights into the specific part of the installation that's failing.
  • Use Debugging Tools: If you are a developer and have access to the source code of the extension, you could try debugging the installation process to pinpoint the exact line of code that's causing the error.

Important Considerations

  • Insiders Builds: Remember that Insiders builds are for testing, and things can break. Be prepared for potential instability.
  • Report the Issue: If you believe there is a bug, please report the issue to the AvaloniaUI and Microsoft teams. The more details you provide, the better chance of a quick fix.

Conclusion

Installing AvaloniaVS on Visual Studio 2026 Insiders can be tricky, but by systematically checking the steps, analyzing the error, and exploring the solutions, you can hopefully get it working. Keep an eye out for updates, and be patient as the Avalonia team and Microsoft work to improve the extension's compatibility with the latest versions of Visual Studio. Good luck and happy coding, guys!