How to pass # character for the $filter to Microsoft Graph?

Question

I try to filter the following user using Microsoft Graph by userPrincipalName:

{
    "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users",
    "value": [
        {
            "businessPhones": [],
            "displayName": "Champi Non Buen Dia",
            "givenName": "buendiachampi",
            "jobTitle": null,
            "mail": "[email protected]",
            "mobilePhone": null,
            "officeLocation": null,
            "preferredLanguage": null,
            "surname": "urrutia",
            "userPrincipalName": "champinon.buendia_champi.com#EXT#@avtestonline.onmicrosoft.com",
            "id": "c6d071ee-5d89-49bb-ac23-768720e5eff4"
        }
    ]
}

When I request with the following URL I get the above JSON result:

https://graph.microsoft.com/v1.0/users?$filter=startswith(userPrincipalName,'champinon.buendia_champi.com')

, but if I add to the filter #EXT# I get a bad request result, how can I pass that character in the filter value?

https://graph.microsoft.com/v1.0/users?$filter=startswith(userPrincipalName,'champinon.buendia_champi.com#EXT#')

The reason why I need to do as is, is that the user must be forced to enter the full username and not a part of it, that #EXT# makes the filtering more accurate, because the username entered in must match with the #EXT#.

Answer 1

The value of #EXT# must be passed encoded as %23EXT%23:

https://graph.microsoft.com/v1.0/users?$filter=startswith(userPrincipalName,'edgardo.urrutia_tcs.com%23EXT%23@')