I am using Azure B2C and I am using the project at https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-devquickstarts-webapp-dotnet as startup guide. I manage to run this sample fine by replacing the config entries with my client ID, tenant ID, etc. However when I try to add Azure B2C authentication to my current web app (Asp.NET MVC dot net 4.5) it behaves in a very weird way. When I press log in it redirects me to a slightly different url than it does in the working sample. It replaces the And sign after the policy with a question mark /authorize?p=b2c_1_signin***?***client_id
This is how the policy url is showing in the Azure B2C portal window: https://login.microsoftonline.com/XXX.onmicrosoft.com/oauth2/v2.0/authorize?p=B2C_1_SignIn&client_id=XXXX&nonce=defaultNonce&redirect_uri=https%3A%2F%2Flocalhost%3A44316%2F&scope=openid&response_type=id_token&prompt=login
However this is the url that my app strangely redirects to: # login.microsoftonline.com/XXX.onmicrosoft.com/oauth2/v2.0/authorize?p=b2c_1_signin?client_id=XXXXX&redirect_uri=https%3a%2f%2flocalhost%3a44316%2f&response_mode=form_post&response_type=id_token&scope=openid&state=OpenIdConnect.AuthenticationProperties%3d1dRzpEoUYWC8q6vPoGU3VtcY7wXXmMDVlkWqr8aQLvWqv64IWeGE0jUnQ6chCZBWEo55uYHsSD27R6EjKIlEaEQWdH6dgIrNDj_n234nLkHb7bKsToir8Yr8j7gbXPb7dBG00wlOufyOfXRT29owsOzjJ8WWwguWDWlo2MN3McsuIWflDKup5qCtQTUS71RBGAEbcQJ_1BqFxIUZsbTglEg4KGm-mroT0tz7PGDcRQU&nonce=636311347285953639.YzQyOWNmYjQtNzAxOS00MTBmLTlkYzQtZGM4MjNlNjdjYThlM2ZlMWMxZGEtYWE0MS00YzY3LWFiM2MtZDgyZWNiNGUxOWQ0
I copied the code exactly from the working sample and it didn't work. I even created a whole new mvc project from scratch and I copied the code from the sample project and it still didn't work. When it redirects to that url it shows 404 - File or directory not found. The resource you are looking for might have been removed, had its name changed, or is temporarily unavailable.
I am pretty sure the answer is quite obvious and I will look very silly but I'm pulling my hair here and any input is really appreciated.
Nevermind guys the problem was resolved by updating Microsoft.IdentityModel.Protocol.Extensions to version 1.0.4.4 or later.
Hope this helps anyone who is still struggling with this.
来源：https://stackoverflow.com/questions/44133401/azure-b2c-getowincontext-authentication-challenge-creates-wrong-url-with-quest