Working with Expressions

Working with Expressions in Aspose.Tasks

Aspose.Tasks for .NET allows you to use Task, Resource, and Project fields in formula expressions.
You can build custom calculations with fields such as:

• Work
• Cost
• Number fields
• DateTime
• Boolean values
• Project-level fields (e.g., Task Count, Resource Count)

These formulas can be applied in Extended Attributes, enabling advanced project customization and reporting.

Using Tasks and Resource Fields in Formula Calculations

The following example shows how task and resource fields can be used in formula-based calculations:

static void Run()
{
    Project project = CreateTestProjectWithCustomField();
    Task task = project.RootTask.Children.GetById(1);

    // Set formula for extended attribute
    ExtendedAttributeDefinition extendedAttributeDefinition1 = project.ExtendedAttributes[0];
    extendedAttributeDefinition1.Alias = "Days from finish to deadline";
    extendedAttributeDefinition1.Formula = "[Deadline] - [Finish]";

    // Set Task Deadline and save project
    Task task = project.RootTask.Children.GetById(1);
    task.Set(Tsk.Deadline, new DateTime(2015, 3, 20, 17, 0, 0));
    project.Save("UsingTasksAndResourceFields_out.mpp", SaveFileFormat.MPP);
}

// Helper method to create project
static Project CreateTestProjectWithCustomField()
{
    // Create new project instance
    Project project = new Project("New Project.mpp");
    project.Set(Prj.StartDate, new DateTime(2015, 3, 6, 8, 0, 0));

    // Add new task with extended attribute
    Task task = project.RootTask.Children.Add("Task");
    ExtendedAttributeDefinition extendedAttributeDefinition = ExtendedAttributeDefinition.CreateTaskDefinition(CustomFieldType.Text, ExtendedAttributeTask.Text5, "My Ext Attr");
    project.ExtendedAttributes.Add(extendedAttributeDefinition);
    ExtendedAttribute extendedAttribute = extendedAttributeDefinition.CreateExtendedAttribute();
    task.ExtendedAttributes.Add(extendedAttribute);

    // Add resource and resource assignment
    Resource resource = project.Resources.Add("Rsc");
    ResourceAssignment assignment = project.ResourceAssignments.Add(task, resource);
    return project;
}

Using Arithmetic Expression

You can define arithmetic expressions to perform calculations between fields:

Project project = CreateTestProjectWithCustomField();

// Set arithmetic formula for extended attribute
ExtendedAttributeDefinition attr = project.ExtendedAttributes[0];
attr.Alias = "Arithmetic Expression";
attr.Formula = "(1+3*(2+ -5)+8/2)^3";

// Display extended attribute value
Task task = project.RootTask.Children.GetById(1);
Console.WriteLine(task.ExtendedAttributes[0].NumericValue);

Using Task Number Fields

Formulas can also reference number fields for flexible computations:

Project project = CreateTestProjectWithCustomField();

// Set formula
ExtendedAttributeDefinition attr = project.ExtendedAttributes[0];
attr.Alias = "Task number fields";
attr.Formula = "([Outline Level] + [Priority] + [% Complete])/2";

Task task = project.RootTask.Children.GetById(1);

// Print extended attribute value before and after updating task percent complete
Console.WriteLine(task.ExtendedAttributes[0].NumericValue);
task.Set(Tsk.PercentComplete, 50);
Console.WriteLine(task.ExtendedAttributes[0].NumericValue);

Formula With Boolean Values

Boolean expressions allow conditional logic within formulas:

Project project = CreateTestProjectWithCustomField();

// Set formula for extended attribute
project.ExtendedAttributes[0].Formula = "[Critical]-[Marked]+4+[Active]-Not [Active]";

// Print value of extended attribute
Task task = project.RootTask.Children.GetById(1);
Console.WriteLine("Formula with boolean values: " + task.ExtendedAttributes[0].TextValue);

Formula With Project Fields

Project-level fields, such as total task count or resource count, can also be included in formulas:

static void Run()
{
    Project project = CreateTestProjectWithCustomFieldWithoutResource();

    // Set formula
    project.ExtendedAttributes[0].Formula = "\"Total tasks: \" & [Task Count] & \" Total resources: \" & [Resource Count]";
    
    // Print if formula value is computed correctly
    Task task = project.RootTask.Children.GetById(1);
    Console.WriteLine("Check Total tasks: 1 Total resources: 0 - {0}", task.ExtendedAttributes[0].TextValue.Equals("Total tasks: 1 Total resources: 0"));
}

static Project CreateTestProjectWithCustomFieldWithoutResource()
{
    Project project = new Project();
    project.Set(Prj.StartDate, new DateTime(2015, 3, 6, 8, 0, 0));
    ExtendedAttributeDefinition attr = ExtendedAttributeDefinition.CreateTaskDefinition(CustomFieldType.Text, ExtendedAttributeTask.Text1, "Custom");
    project.ExtendedAttributes.Add(attr);
 
    Task task = project.RootTask.Children.Add("Task");
    ExtendedAttribute a = attr.CreateExtendedAttribute();
    task.ExtendedAttributes.Add(a);
    return project;
}