UserInfo endpoint does not output StringCollection claims correctly

Question

UserInfo endpoint does not output StringCollection claims correctly

Craig Evans 11

I have implemented a UserInfo Endpoint for a RelyingParty in my B2C Tenant. The string claims output correctly, but the StringCollection claims are issued as System.Collections.Generic.List1[System.String]

It's not possible to output a JSON array using string transformations. The best I can do is something like this: "groups": "[\"group1\","\group2\"]"

Obviously this won't work with the relying party. According to https://github.com/MicrosoftDocs/azure-docs/issues/75344 this was fixed/closed over a year ago, but it was never actually fixed.

Anonymous

2022-09-28T20:02:21.473+00:00

Hi @Craig Evans , thanks for letting us know about this. I'll reopen the issue and reach out to find out some more information.

Best,
James
Craig Evans 11 Reputation points

2022-10-04T16:23:48.12+00:00

Thanks @James Hamil . Sorry about the multiple avenues of reaching out. I wasn't sure what was the appropriate route. We have a client that needs the UserInfo endpoint to return groups as a proper JSON array. I'm able to get the groups out of B2C using the graph API, but when attempting to send the claims in the UserInfo endpoint it doesn't output them correctly.
Craig Evans 11 Reputation points

2022-10-10T18:34:03.937+00:00

@James Hamil any updates on this?
Paul Kirwan 0 Reputation points

2024-03-28T17:45:13.4+00:00

@James Hamil can you provide an update on this bug?
Matthieu 0 Reputation points

2025-10-30T20:32:33.49+00:00

In case someone is still listening to this post 3 years later: this bug is still present. Did anyone find out how to get the real string collection, and not "System.Collections.Generic.List`1[System.String]"?

Your answer

Anonymous

2022-09-28T20:02:21.473+00:00

Hi @Craig Evans , thanks for letting us know about this. I'll reopen the issue and reach out to find out some more information.

Best,
James
Craig Evans 11 Reputation points

2022-10-04T16:23:48.12+00:00

Thanks @James Hamil . Sorry about the multiple avenues of reaching out. I wasn't sure what was the appropriate route. We have a client that needs the UserInfo endpoint to return groups as a proper JSON array. I'm able to get the groups out of B2C using the graph API, but when attempting to send the claims in the UserInfo endpoint it doesn't output them correctly.
Craig Evans 11 Reputation points

2022-10-10T18:34:03.937+00:00

@James Hamil any updates on this?
Paul Kirwan 0 Reputation points

2024-03-28T17:45:13.4+00:00

@James Hamil can you provide an update on this bug?
Matthieu 0 Reputation points

2025-10-30T20:32:33.49+00:00

In case someone is still listening to this post 3 years later: this bug is still present. Did anyone find out how to get the real string collection, and not "System.Collections.Generic.List`1[System.String]"?