Microsoft.IdentityModel.Clients.ActiveDirectory.TokenResponse反序列化错误“遇到意外的字符'<'”

Question

I'm using the sample code from https://github.com/Azure-Samples/active-directory-b2c-dotnet-webapp-and-webapi . When I receive an authorization code the method ConfidentialClientApplication.AcquireTokenByAuthorizationCodeAsync in the callback method OnAuthorizationCodeReceived throws the exception:

System.Runtime.Serialization.SerializationException: There was an error deserializing the object of type Microsoft.Identity.Client.Internal.OAuth2.TokenResponse. Encountered unexpected character '<'.

Here's a snippet of the sample code:

/*
 * Callback function when an authorization code is received 
 */
private async Task OnAuthorizationCodeReceived(AuthorizationCodeReceivedNotification notification)
{
    // Extract the code from the response notification
    var code = notification.Code;

    string signedInUserID = notification.AuthenticationTicket.Identity.FindFirst(ClaimTypes.NameIdentifier).Value;
    TokenCache userTokenCache = new MSALSessionCache(signedInUserID, notification.OwinContext.Environment["System.Web.HttpContextBase"] as HttpContextBase).GetMsalCacheInstance();
    ConfidentialClientApplication cca = new ConfidentialClientApplication(ClientId, Authority, RedirectUri, new ClientCredential(ClientSecret), userTokenCache, null);
    try
    {
        AuthenticationResult result = await cca.AcquireTokenByAuthorizationCodeAsync(code, Scopes);
    }
    catch (Exception ex)
    {
        //TODO: Handle
        throw;
    }
}

Answer 1

The issue was that the Authority URL that was being passed to ConfidentialClientApplication was invalid and was returning a HTTP 404 not found error. The Authority URL is created using the Tenant and DefaultPolicy values. In my case the Tenant and DefaultPolicy properties were being initialized after the Authority property resulting in the URL to not contain the proper values.

public static string Authority = String.Format(AadInstance, Tenant, DefaultPolicy);
...
public static string Tenant = ConfigurationManager.AppSettings["ida:Tenant"];
public static string DefaultPolicy = SignUpSignInPolicyId;

This resulted in the Authority URL to have the value: https://login.microsoftonline.com/tfp///v2.0/.well-known/openid-configuration

vs

https://login.microsoftonline.com/tfp/my_tenant.onmicrosoft.com/my_policy/v2.0/.well-known/openid-configuration

During my initial search I found this issue reported to https://github.com/AzureAD/azure-activedirectory-library-for-dotnet/issues/720 but no solution. I've posted my answer there to help anyone in the future.