How to solve “System.TypeInitializationException: ‘The type initializer for ‘WinRT.ActivationFactory`1’ threw an exception.'” in the MAUI application?

This post was most recently updated on July 27th, 2024.

… or “How to bang your head on a wall for hours on end when developing a MAUI application?” 😂

This article explains how to fix a surprising error you might get when trying to run a MAUI app in Windows. For me, it was thrown when I was simply reading a file from the disk, but I suspect the same or similar error (“System.TypeInitializationException: ‘The type initializer for ‘WinRT.ActivationFactory`1′ threw an exception.’ – COMException: ClassFactory cannot supply requested class”) can probably be thrown for other reasons as well.

Anyway – let’s take a closer look at the issue and when it was thrown for me, shall we?

Problem

The error gets thrown at perhaps the unlikeliest part of your code ever. When you’re reading a file with System.IO.File on Windows. Like – shouldn’t System.IO stuff work in platform-specific MAUI builds? And it works just fine on Android. But on Windows, this code throws:

using Stream fileStream = System.IO.File.OpenRead(filePath);
using StreamReader reader = new StreamReader(fileStream);
var c = await reader.ReadToEndAsync();

And the error you get is a pretty drastic one:

System.TypeInitializationException: 'The type initializer for 'WinRT.ActivationFactory`1' threw an exception.'

COMException: ClassFactory cannot supply requested class

Perhaps you can get similar errors for different reasons, too. But I suspect the fix might quite often be the same, as far as you’re trying to build stuff with MAUI.

Okay – so what to do to fix the issue at hand?

Solution

Annoying, but I haven’t found the proper fix to this. That’s not to say I wouldn’t have got a pretty good set of workarounds documented below for trying out! 😁

Hope this helps! If you’ve figured out other ways to fix this, let me know in the comments section below!

References

A couple of sources I found useful in the investigation:

• https://learn.microsoft.com/en-us/dotnet/core/tools/dotnet-workload-install
• https://learn.microsoft.com/en-us/answers/questions/1087945/there-is-no-runtime-pack-availabel-for-microsoft-a
• https://learn.microsoft.com/en-us/windows/apps/package-and-deploy/project-properties

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Antti K. Koskela

Developer / Speaker / Consultant at Koskila / Precio Fishbone / Norppandalotti Software Co / Alter - Experience Ideas Ltd

Antti Koskela is a proud digital native nomadic millennial full stack developer (is that enough funny buzzwords? That's definitely enough funny buzzwords!), who works as Solutions Architect for Precio Fishbone, building delightful Digital Workplaces.

He's been a developer from 2004 (starting with PHP and Java), and he's been working on .NET projects, Azure, Office 365, SharePoint and a lot of other stuff. He's also Microsoft MVP for Azure.

This is his personal professional (e.g. professional, but definitely personal) blog.

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