I’ve recently decided to switch from string to GUID as the unique identifier for the IdentityUser. I have successfully applied the migration to the database, but now the UserManager methods don’t work anymore. Finding a user by email with the DbContext works fine (DataContext.Users.SingleAsync(...)) but returns null with UserManager(UserManager.FindByIdAsync(...))

ApplicationUser:

public class ApplicationUser : IdentityUser<Guid>
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public override Guid Id { get; set; }
}

DbContext:

public class DataContext :
    IdentityDbContext<ApplicationUser, IdentityRole<Guid>, Guid, IdentityUserClaim<Guid>, IdentityUserRole<Guid>, IdentityUserLogin<Guid>, IdentityRoleClaim<Guid>, IdentityUserToken<Guid>>,
    IDataContext
{
    private readonly IUserContextAccessor _userContextAccessor;

    public DataContext(DbContextOptions<DataContext> options, IUserContextAccessor userContextAccessor) : base(options)
    {
        _userContextAccessor = userContextAccessor;
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);
    }
}

Profile Service (I get the error inside the IsActiveAsync method)

public class ProfileService : IProfileService
{
    private readonly IUserClaimsPrincipalFactory<ApplicationUser> _claimsFactory;
    private readonly UserManager<ApplicationUser> _userManager;

    public ProfileService(
        UserManager<ApplicationUser> userManager,
        IUserClaimsPrincipalFactory<ApplicationUser> claimsFactory)
    {
        _userManager = userManager;
        _claimsFactory = claimsFactory;
    }

    public async Task GetProfileDataAsync(ProfileDataRequestContext context)
    {
        ...
    }

    public async Task IsActiveAsync(IsActiveContext context)
    {
        var sub = context.Subject.GetSubjectId();
        var user = await _userManager.FindByIdAsync(sub);
        context.IsActive = user != null;
    }
}

And finally, I register it like this:

 services.AddIdentity<ApplicationUser, IdentityRole<Guid>>(options =>
            {
                options.User.RequireUniqueEmail = true;
            })
            .AddEntityFrameworkStores<DataContext>()
            .AddDefaultTokenProviders();