// Set constraint Must Start On for task with Id 5
System::SharedPtr<Task> roof = project1->get_RootTask()->get_Children()->GetById(5);
roof->Set<ConstraintType>(Tsk::ConstraintType(), Aspose::Tasks::ConstraintType::MustStartOn);
roof->Set(Tsk::ConstraintDate(), System::DateTime(2017, 1, 1, 9, 0, 0));
    
// Save project as pdf
System::SharedPtr<SaveOptions> options = System::MakeObject<PdfSaveOptions>();
options->set_StartDate(project1->Get<System::DateTime>(Prj::StartDate()));
options->set_Timescale(Aspose::Tasks::Visualization::Timescale::ThirdsOfMonths);
project1->Save(dataDir + u"project_MustStartOn_out.pdf", options);