static void Main(string[] args) { ProjectReader reader = new ProjectReader(); Project project = reader.Read("Project.mpp"); Aspose.Tasks.Task task = new Aspose.Tasks.Task("Task1"); task.ActualStart = DateTime.Parse("23-Aug-2012"); //Set duration in hours task.Duration = new TimeSpan(24, 0, 0); task.DurationFormat = TimeUnitType.Day; project.RootTask.Children.Add(task); //Recalculate task IDs project.CalcTaskIds(); project.CalcTaskUids(); //Save the Project as XML project.Save("OutputProject.xml", Aspose.Tasks.Saving.SaveFileFormat.XML); }