To authenticate users of an ASP.NET application using Azure Active Directory, what is the first configuration step to perform in Azure AD?

To integrate an application with Azure Active Directory (Azure AD) for authentication, the first crucial step is to create an app registration. This process registers your application with Azure AD, establishing an identity for it. During app registration, you define properties like the application's name, supported account types, and redirect URIs, which Azure AD uses to return tokens after authentication. Without an app registration, Azure AD has no record of your application and cannot issue tokens for it. Assigning an enterprise application to users and groups happens after the app is registered. Configuring SAML is for specific authentication flows, not the initial setup. Creating an OAuth token is an outcome of a successful authentication flow, not a configuration step. A membership database in Azure SQL is for application-specific user management, not Azure AD authentication.