var workflow = new WorkFlow<SignInContext>()
            .AddStep<VerifyUsernameExistande, bool>(b => b.When(false).AddStep<ErrorMessage>().Stop())
            .AddStep<VerifyCredentials, bool>(b => {
                b.When(false).AddStep<ErrorMessage>();
                b.Otherwise()
                    .AddStep<PutInSession>()
                    .AddStep<LogToDatabase>();
            });

        workflow.Execute();