We have an application where we store users login name in the format domain\username. We authenticate via windows and then get additional info from our database by matching the domain\username we get from the user to our database.
Now they want to move to the cloud. We authenticate users via apps in Azure AD. However, the user identifier we get back is first.last@domain.com.
I have fiddled around with https://graph.microsoft.com/v1.0/users/email and the select command to try and get the 'old' name. Howev,er I have not yet found out how to get it.
The reason they move to the cloud is that they are merging two ADs. So some users will be DomainA and some DomainB, but in the same tenant. So my first thought was to try and convert the mail to the other format. However, the two different ADs have different naming standards. One has DOMAINA\fila (two first letters from the first name and two first letters from the last name) and the other one has DOMAINB\firlas. Also it feels really ugly to try and solve it that way.
Is it possible to fetch the users loginname formatted as domain\username via Microsoft Graph?
Using the beta edition of Graph, you can obtain the user's domain and username from the onPremisesDomainName and onPremisesSamAccountName properties:
/beta/users?$select=userPrincipalName,onPremisesDomainName,onPremisesSamAccountName
The domain is stored as a FQDN so you'll need to do some translation. For example, domainName.ad.contoso.com might translate to domainName\).
This will give you a workaround so you can match up users with your internal databases. It is however only a temporary solution. Long-term, you really want to migrate to using the userPrincipalName. This is the primary user identifier and guaranteed to be unique within a given tenant.
Azure AD is a little different than the legacy Active Directory. Certain concepts from legacy AD such as Organizational Units (OUs), Group Policy Objects (GPOs), Kerberos Authentication, Lightweight Directory Access Protocol (LDAP), Domain trusts between multiple domains, and several others simply do not exist in the cloud.