We have two projects; one's a VSTO Add-in and the other is a TypeLibrary which exposes Outlook COM Interop calls by registering the assembly as a set of COM interfaces.

This setup has allowed us to communicate with Office products (Excel, word, and Outlook) from our old C++ executable. This has been working fine for nearly 10 years.

We've tried adding some Graph API calls and we're getting the following exception:

Exception thrown: 'System.InvalidOperationException' in Microsoft.Identity.Client.Extensions.Msal.dll

The graph api sdk calls I'm making work perfectly fine when in their own projects (e.g. .NET Core) as a class Library. However, when I add that working class library project to my legacy projects, I get the problems above.

Code Being Executed

await graphClient.Me.Request().GetAsync();