How do i include email in the redirect to AZURE AD B2C

Question

I have set up an Azure B2C tenant and used custom policies to add azure ad as an IDP so that users can sign up with their domain accounts. I can build a custom page where ask them for their email and then redirect them to the proper policy(one for work domain accounts and another for personal emails), so that they do not have to make the choice between work and personal emails. The problem is that I do not want to make the user enter the email once again. Is there a way/option to do this? I basically want to achieve something similar to what the common endpoint of Azure AD does for all accounts.

Answer 1

For a custom policy, if you add the "login_hint" query string parameter to the OpenID Connect authentication request, then you can default the login field to this login hint by adding the "DefaultValue" attribute to the "signInName" input claim for the "SelfAsserted-LocalAccountSignin-Email" technical profile as follows:

<TechnicalProfile Id="SelfAsserted-LocalAccountSignin-Email">
  <DisplayName>Local Account Signin</DisplayName>
  ...
  <InputClaims>
    <InputClaim ClaimTypeReferenceId="signInName" DefaultValue="{OIDC:LoginHint}" />
  </InputClaims>
  <OutputClaims>
    <OutputClaim ClaimTypeReferenceId="signInName" Required="true" />
    ...
  </OutputClaims>
  ...
</TechnicalProfile>

The "DefaultValue" attribute references a claims resolver that sets the "signInName" claim type to the "login_hint" parameter of the OpenID Connect authentication request.

See the Set up direct sign-in using Azure Active Directory B2C article for more information about passing the "login_hint" query string parameter.