Could not load file or assembly 'Microsoft.Extensions.Configuration.Abstractions, Version=5.0.0.0 in Azure Functions

Question

I have an API and a separate Azure Functions app. I upgraded my API app to .NET 5 and it's working fine. In the API app's solution, I have class library projects that I also reference in my Azure Functions app. These class libraries are netstandard2.1 projects.

Ever since this update -- during which I also updated all my NuGet packages to latest versions -- my Azure Functions app stopped working. I'm getting the following error:

Could not load file or assembly 'Microsoft.Extensions.Configuration.Abstractions, Version=5.0.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60'. The system cannot find the file specified. Value cannot be null. (Parameter 'provider')

I noticed that there were breaking changes involving the Microsoft.Extensions.* packages and their recommendation is to install the package that is causing the issue directly. So I added Microsoft.Extensions.Configuration.Abstractions to my Azure Functions manually -- before it was being installed as a dependency of Microsoft.Extensions.Configuration package. Here's the information about this: https://github.com/dotnet/aspnetcore/issues/21033

The issue still persists. I even tried downgrading Microsoft.Extensions.Configuration in both the API and Functions app, but I'm still getting the same error.

Any idea how to resolve this issue?

Answer 1

Sam's comment should be accepted as correct answer. I try it out to downgrade Microsoft.Extensions* (in my case Microsoft.Extensions.Logging.Console) from 5.0.0 to 3.1.0 and the error just gone. Bravo!

Answer 2

As a reference, this GitHub link explains exactly why that happens.

And as of now, you either track down the exact versions been referenced or downgrade everything to the latest v3 build.

In a nutshell, Azure Functions SDK already has some dependencies loaded in memory, so your libraries cannot use newer versions of the same libraries.