Editing custom Azure B2C attributes using Microsoft Graph Explorer - azure

Question

I am trying to use the Microsoft Graph Explorer to update a custom attribute I created in B2C named GroupID.
First, I get the id of the user I want to edit using this query:
GET https://graph.microsoft.com/v1.0/{myResourceName}.onmicrosoft.com/users
This returns the following JSON:
{
"#odata.context": "https://graph.microsoft.com/v1.0/$metadata#users",
"value": [
{
"displayName": "User Name",
"surname": "Name",
"givenName": "User",
"id": "ff46335221e1a365",
"userPrincipalName": "user#username.com",
"businessPhones": [],
"jobTitle": null,
"mail": null,
"mobilePhone": null,
"officeLocation": null,
"preferredLanguage": null
}
]
}
Now I'd like to add a value for GroupID for this user. The attribute itself does not appear in the above JSON, presumably because it does not yet have a value assigned.
I tried using this query:
PATCH https://graph.microsoft.com/v1.0/{myResourceName}.onmicrosoft.com/users/ff46335221e1a365
With request body:
{"GroupID": 1234}
But I get a 405 error:
The method or operation is not allowed.
Am I using the wrong query? I tried to follow the guide here.
UPDATE
Attached is a screenshot of the request. In this screenshot, I omitted the {myResourceName}.onmicrosoft.com from the URL. But I've tried both ways and still get the 405 error.

Answer 1

Please see this document:
Extension attributes in the Graph API are named by using the
convention extension_ApplicationClientID_attributename, where the
ApplicationClientID is the Application (client) ID of the
b2c-extensions-app application (found in App registrations > All
Applications in the Azure portal). Note that the Application (client)
ID as it's represented in the extension attribute name includes no
hyphens. For example:
"extension_831374b3bd5041bfaa54263ec9e050fc_loyaltyNumber": "212342"
So the real custom attribute name is extension_{ApplicationClientID}_GroupID.
Go to Azure AD -> App registrations to find the application id of the b2c-extensions-app application.
The {ApplicationClientID} is the application id without hyphens.
PATCH https://graph.microsoft.com/v1.0/users/ff46335221e1a365
{"extension_{ApplicationClientID}_GroupID": 1234}