protected readonly IPrincipal _principal ;

    public MyDbContext(DbContextOptions<MyDbContext> options, IPrincipal principal) : base(options)
    {
        _principal = principal;
    }

    public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken = default(CancellationToken))
    {
        // Do something with Claim value...
        await base.SaveChangesAsync(cancellationToken);
    }

public async Task<ClaimsPrincipal> TransformAsync(ClaimsPrincipal principal)
    {
        // Add Claims...
        return principal;
    }