Add TenantId configuration instruction to Azure AD B2C docs (#36814)

* Initial plan

* Add TenantId instruction to Azure AD B2C configuration docs

Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>

* Clarify Tenant ID retrieval process in documentation

Updated instructions for obtaining Tenant ID in Azure AD B2C.

* Apply suggestions from code review

Co-authored-by: Wade Pickett <wpickett@microsoft.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>
Co-authored-by: Meaghan Osagie (Lewis) <mosagie@microsoft.com>
Co-authored-by: Wade Pickett <wpickett@microsoft.com>

Author: 3 people

aspnetcore/security/authentication/azure-ad-b2c.md

@@ -4,7 +4,7 @@ author: guardrex
 description: Discover how to set up Azure Active Directory B2C authentication with ASP.NET Core.
 ms.author: wpickett
 ms.custom: "devx-track-csharp, mvc"
-ms.date: 01/22/2026
+ms.date: 02/27/2026
 uid: security/authentication/azure-ad-b2c
 ---
 # Cloud authentication with Azure Active Directory B2C in ASP.NET Core
@@ -16,7 +16,7 @@ By [Damien Bod](https://github.com/damienbod)
 [Azure Active Directory B2C](/azure/active-directory-b2c/active-directory-b2c-overview) (Azure AD B2C) is a cloud identity management solution for web and mobile apps. The service provides authentication for apps hosted in the cloud and on-premises. Authentication types include individual accounts, social network accounts, and federated enterprise accounts. Additionally, Azure AD B2C can provide multi-factor authentication with minimal configuration.
 
 > [!TIP]
-> Microsoft Entra ID, Microsoft Entra External ID and Azure AD B2C are separate product offerings. An Entra ID tenant generally represents an organization, while an Azure AD B2C tenant or a Microsoft Entra External ID  tenant can represent a collection of identities to be used with relying party applications. To learn more, see [Azure AD B2C: Frequently asked questions (FAQ)](/azure/active-directory-b2c/active-directory-b2c-faqs).
+> Microsoft Entra ID, Microsoft Entra External ID and Azure AD B2C are separate product offerings. An Entra ID tenant generally represents an organization, while an Azure AD B2C tenant or a Microsoft Entra External ID tenant can represent a collection of identities to be used with relying party applications. To learn more, see [Azure AD B2C: Frequently asked questions (FAQ)](/azure/active-directory-b2c/active-directory-b2c-faqs).
 
 > [!TIP]
 > [Microsoft Entra External ID for customers](/azure/active-directory/external-identities/customers/overview-customers-ciam) is Microsoft’s new customer identity and access management (CIAM) solution.
@@ -68,6 +68,7 @@ In this tutorial, you'll learn how to configure an ASP.NET Core app for authenti
     * For **Domain**, use the domain of your Azure AD B2C tenant.
     * For **ClientId**, use the **Application (client) ID** from the app registration you created in your tenant.
     * For **Instance**, use the domain of your Azure AD B2C tenant.
+    * For **TenantId**, use the **Tenant ID** from your Azure AD B2C tenant. In the Azure portal, search for and select **Microsoft Entra ID**. In the **Overview**, copy the **Tenant ID**.
     * For **SignUpSignInPolicyId**, use the user flow policy defined in the Azure B2C tenant
 	* Use either the **ClientSecret** or the **ClientCertificates** configuration. ClientCertificates are recommended.
     * Leave all other values as they are.
@@ -102,7 +103,7 @@ In this tutorial, you'll learn how to configure an ASP.NET Core app for authenti
 
         In the preceding code:
 
-        * Calls to the `AddAuthentication` and `AddMicrosoftIdentityWebApp` methods configure the app to use Open ID Connect, specifically configured for the Microsoft identity platform.
+        * Calls to the `AddAuthentication` and `AddMicrosoftIdentityWebApp` methods configure the app to use OpenID Connect, specifically configured for the Microsoft identity platform.
         * `AddAuthorization` initializes ASP.NET Core authorization.
         * The `AddRazorPages` call configures the app so anonymous browsers can view the Index page. All other requests require authentication.
         * `AddMvcOptions` and `AddMicrosoftIdentityUI` add the required UI components for redirecting to/from Azure AD B2C.
@@ -116,7 +117,7 @@ In this tutorial, you'll learn how to configure an ASP.NET Core app for authenti
 ## Run the app
 
 > [!NOTE]
-> Use the profile which matches the Azure App registration **Redirect URIs**
+> Use the profile which matches the Azure App registration **Redirect URIs**.
 1. Run the app.
     
     ```dotnetcli