DHTMLX Planning Engine Documentation

Note#

A non-fatal note about the input of a scheduling call: a task, link or assignment that was left out of the plan, or a field that repair validation changed. Notes are listed in ScheduleResult.Notes. Nothing is thrown for them.

Note is a closed union: an abstract record with one sealed record per variant. Read it with switch pattern matching on the nested types. The records are immutable and compare by value.

Declaration#

namespace Plen;

public abstract record Note
{
    public sealed record DroppedLink(Id Link, string Reason) : Note;
    public sealed record DroppedTask(Id Task, string Reason) : Note;
    public sealed record DroppedAssignment(Id Assignment, string Reason) : Note;
    public sealed record Repaired(string Path, string Message) : Note;
}

The constructor of Note is private, so these four records are the only variants.

Variants#

Variant When it occurs
DroppedLink A link isn't part of the plan, for example because one of its tasks is unscheduled.
DroppedTask A task isn't part of the plan because it's unscheduled.
DroppedAssignment An assignment isn't part of the plan because its task is unscheduled.
Repaired Validation.Repair changed an input field. 
public sealed record DroppedLink(Id Link, string Reason) : Note;
Property Type Description
Link Id Id of the dropped link.
Reason string Human-readable reason, e.g. target task "3" is unscheduled.

DroppedTask#

public sealed record DroppedTask(Id Task, string Reason) : Note;
Property Type Description
Task Id Id of the dropped task.
Reason string Human-readable reason: unscheduled.

A task is unscheduled when TaskData.Unscheduled is true.

DroppedAssignment#

public sealed record DroppedAssignment(Id Assignment, string Reason) : Note;
Property Type Description
Assignment Id Id of the dropped assignment.
Reason string Human-readable reason, e.g. task "3" is unscheduled.

Repaired#

public sealed record Repaired(string Path, string Message) : Note;
Property Type Description
Path string Input path of the changed field, in wire spelling, e.g. tasks[1].start_date.
Message string What was wrong and how it was fixed.

Only a project created with Validation.Repair reports Repaired notes. The list of fixes and their paths is on Validation.

Example#

using Plen;

var monday = Moment.FromYmdHm(2026, 8, 10, 8, 0) ?? throw new InvalidOperationException("invalid date");

var data = new ProjectData
{
    Tasks =
    [
        new TaskData(1) { StartDate = monday, Duration = 1.0 },
        new TaskData(2) { StartDate = monday, Duration = 1.0, Unscheduled = true },
    ],
    Links =
    [
        new LinkData { Id = 10, Source = 1, Target = 2 },
    ],
};

var result = Engine.Schedule(data, new SolveOptions());

foreach (var note in result.Notes)
{
    var line = note switch
    {
        Note.DroppedLink n => $"link {n.Link} dropped: {n.Reason}",
        Note.DroppedTask n => $"task {n.Task} dropped: {n.Reason}",
        Note.DroppedAssignment n => $"assignment {n.Assignment} dropped: {n.Reason}",
        Note.Repaired n => $"repaired {n.Path}: {n.Message}",
        _ => note.ToString(),
    };
    Console.WriteLine(line);
}
// task 2 dropped: unscheduled
// link 10 dropped: target task "2" is unscheduled