Adding a user with custom claim - azure-ad-b2c

Question

I'm having an issue adding a user to Azure B2C via the Microsoft Graph Api with a custom claim. I have added a claim called "sample", and when I add a user via the registration that claim will be populated with the value that I enter.
However, I need to add users via code not with self-registration. I have the following code that will add a user
// create the connection
var confidentialClientApplication = ConfidentialClientApplicationBuilder
.Create(clientId)
.WithTenantId(tenantId)
.WithClientSecret(clientSecret)
.Build();
var authProvider = new ClientCredentialProvider(confidentialClientApplication);
var client = new GraphServiceClient(authProvider);
var user = new User
{
AccountEnabled = true,
DisplayName = "John Smith",
UserPrincipalName = $"john.smith#{tenantId}",
MailNickname = "john.smith",
PasswordProfile = new PasswordProfile
{
ForceChangePasswordNextSignIn = false,
Password = "P#ssword1"
},
};
var addedUser = await client.Users.Request().AddAsync(user);
This is the same, but using HTTP direct. Which again will add the users
POST /v1.0/users HTTP/1.1
Host: graph.microsoft.com
SdkVersion: postman-graph/v1.0
Content-Type: application/json
Authorization: Bearer [redacted]
User-Agent: PostmanRuntime/7.20.1
Accept: */*
Cache-Control: no-cache
Postman-Token: [redacted]
Host: graph.microsoft.com
Accept-Encoding: gzip, deflate
Content-Length: 325
Connection: keep-alive
cache-control: no-cache
{
"accountEnabled": true,
"displayName": "Joe Blogs",
"mailNickname": "joe.blogs",
"userPrincipalName": "joe.blogs#[redacted].onmicrosoft.com",
"passwordProfile": {
"forceChangePasswordNextSignIn": true,
"password": "P#ssword1"
},
"passwordPolicies": "DisablePasswordExpiration"
}
As I say the above code will add a user, but I can't figure out how to add the custom claim at the same time. The first set of code is using the Microsoft.Graph nuget package. The second is taken from a direct http call in Postman.
I seem to be going round in circles when reading the documentation, can can't seem to see how to do it in the new B2C v2.
Anyone, any idea?
Cheers

Answer 1

Ok worked out how to do this. Need to add the user like above, then update it with the custom claim. They key is that claim has the name in the format of
extension_xxxxx_sample
Where the xxxxx has the application id of the b2c-extensions-app application, which is a in build application.
So once the user has been added then the following code will add the custom claim
var confidentialClientApplication = ConfidentialClientApplicationBuilder
.Create(clientId)
.WithTenantId(tenantId)
.WithClientSecret(clientSecret)
.Build();
var authProvider = new ClientCredentialProvider(confidentialClientApplication);
var client = new GraphServiceClient(authProvider);
var dictionary = new Dictionary<string, object>();
dictionary.Add("extension_xxxxx_sample", "abcd");
await client.Users[$"john.smith#{tenantId}"]
.Request()
.UpdateAsync(new User()
{
AdditionalData = dictionary
});
The key is that the b2c-extensions-app may have the application id of 7e4ff0cd-825a-47ba-a08c-b13a4244b4ce. However, you would add the claim with the following
extension_7e4ff0cd825a47baa08cb13a4244b4ce_sample
not with
extension_7e4ff0cd-825a-47ba-a08c-b13a4244b4ce_sample