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Well, that title is a mouthful. But it’s the topic for today, so what can you do?

That said, this article should be pretty topical, as the issue started popping up only a few days ago. Chances are it’ll be patched soon enough, but in the meantime, it’s always useful to document the fix!

Problem

Table of Contents

When running or debugging Azure Functions locally, your runtime just blurts our this error and fails to compile your functions:

[2021-01-11T10:28:11.495Z] A host error has occurred during startup operation '0d00defa-b8bd-4fb8-9794-b0e5950a4c38'.
[2021-01-11T10:28:11.499Z] System.IO.FileSystem: Could not find a part of the path 'C:\Users\username\AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers'.
Value cannot be null. (Parameter 'provider')
Press any to continue….[2021-01-11T10:28:12.625Z] A host error has occurred during startup operation 'beca4180-a97c-4fab-b3d8-2323dbf5512d'.
[2021-01-11T10:28:12.628Z] System.IO.FileSystem: Could not find a part of the path 'C:\Users\username\AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers'.
[2021-01-11T10:28:14.762Z] A host error has occurred during startup operation '447864ad-026f-462d-9d8d-70f95703baa8'.
[2021-01-11T10:28:14.764Z] System.IO.FileSystem: Could not find a part of the path 'C:\Users\username\AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers'.

And this is how it actually looks like:

"System.IO.FileSystem: Could not find a part of the path \AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers. Value cannot be null. (Parameter 'provider')" getting thrown when running Azure Functions locally. — “System.IO.FileSystem: Could not find a part of the path \AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers. Value cannot be null. (Parameter ‘provider’)” getting thrown when running Azure Functions locally.

What do?

Solution

This one turned out to be easy to fix.

Time needed: 2 minutes.

How to fix “System.IO.FileSystem: Could not find a part of the path \AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers. Value cannot be null. (Parameter ‘provider’)” when running Azure Functions locally?

Copy-paste the path the CLI is complaining about
That’s going to be something along the lines of:
‘C:\Users\your username here\AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers
Remove the last part (workers) and open the directory in File Explorer
Create a new folder called “workers”
It doesn’t matter if it’s empty. No need to copy anything over from previous AzureFunctionsTools (although you can, if you really want to). You just need a new empty folder named “workers”.
Run your functions again -> works like magic

And that’s about it!

References

https://developercommunity.visualstudio.com/content/problem/1304718/azure-functions-local-debugging-broke-with-3170-up.html

Author
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Antti K. Koskela

Developer / Architect / Consultant at Koskila / Valo Solutions Ltd. / 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 a Solutions Architect for Valo Intranet, the product that will make you fall in love with your intranet.

He's been a developer from 2004 (starting with PHP and Java), and he's been bending and twisting SharePoint into different shapes since MOSS. Nowadays he's not only working on SharePoint, but also on .NET projects, Azure, Office 365 and a lot of other stuff. He's also Microsoft MVP for Office Development.

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

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How to fix “System.IO.FileSystem: Could not find a part of the path \AppData\Local\AzureFunctionsTools\Releases\3.17.0\workers. Value cannot be null. (Parameter ‘provider’)” when running Azure Functions locally?

Problem

Solution

References

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