Project project = new Project("New Project.mpp")
{
    CalculationMode = CalculationMode.Automatic
};

project.Set(Prj.DateFormat, DateFormat.DateDddMmDdYy);
project.Set(Prj.StartDate, new DateTime(2019, 9, 16, 9, 0, 0));
project.Set(Prj.NewTasksAreManual, false);
project.Set(Prj.ActualsInSync, false);

Resource workResource = project.Resources.Add("Servente (Work)");
workResource.Set(Rsc.Name, "Servente (Work)");
workResource.Set(Rsc.Initials, "S");
workResource.Set(Rsc.Type, ResourceType.Work);
workResource.Set(Rsc.StandardRateFormat, RateFormatType.Hour);
workResource.Set(Rsc.Code, "1503");

Resource materialResource = project.Resources.Add("Tijolo (Material)");
materialResource.Set(Rsc.Name, "Tijolo (Material)");
materialResource.Set(Rsc.Initials, "T");
materialResource.Set(Rsc.Type, ResourceType.Material);
materialResource.Set(Rsc.StandardRateFormat, RateFormatType.MaterialResourceRate);
materialResource.Set(Rsc.Code, "21341");

Task task1 = project.RootTask.Children.Add("Task - 01");
task1.Set(Tsk.IsRollup, new NullableBool(true));
task1.Set(Tsk.IsPublished, new NullableBool(false));
Task task2 = task1.Children.Add("Task - 01.01");
task2.Set(Tsk.IsRollup, new NullableBool(true));
task2.Set(Tsk.IsPublished, new NullableBool(false));
Task task3 = task2.Children.Add("Task - 01.01.001");
task3.Set(Tsk.IsEstimated, new NullableBool(false));
task3.Set(Tsk.Start, new DateTime(2019, 9, 16, 9, 0, 0));
task3.Set(Tsk.Duration, project.GetDuration(10, TimeUnitType.Day));
task3.Set(Tsk.Work, project.GetDuration(10, TimeUnitType.Day));
task3.Set(Tsk.IsRollup, new NullableBool(true));
task3.Set(Tsk.IsPublished, new NullableBool(false));

ResourceAssignment assignment1 = project.ResourceAssignments.Add(task3, materialResource);
assignment1.Set(Asn.Delay, project.GetDuration(40, TimeUnitType.Hour));
assignment1.Set(Asn.Start, new DateTime(2019, 9, 23, 9, 0, 0));
assignment1.Set(Asn.Finish, new DateTime(2019, 9, 27, 18, 0, 0));
ResourceAssignment assignment2 = project.ResourceAssignments.Add(task3, workResource);
assignment2.Set(Asn.Work, project.GetDuration(56, TimeUnitType.Hour));
assignment2.Set(Asn.Start, new DateTime(2019, 9, 16, 9, 0, 0));
assignment2.Set(Asn.Finish, new DateTime(2019, 9, 24, 18, 0, 0));

// to match expected MPP fully
assignment2.Set(Asn.WorkContour, WorkContourType.Contoured);
task3.Set(Tsk.IsManual, new NullableBool(true));
task1.Set(Tsk.IsManual, new NullableBool(true));

project.Save("Assignment_Dates.mpp", SaveFileFormat.MPP);