Load all task dates#

Get the start, end and duration of every scheduled task from one solve, for example to fill your UI when a project first opens.

By default, Updates in a ScheduleResult is sparse: it lists only the tasks that moved. Set SolveOptions.IncludeUnchanged and the same solve also reports the tasks that didn't move. You don't need a separate call.

Steps#

1. Create the solve options with IncludeUnchanged set to true:

   Copy

   var options = new SolveOptions { IncludeUnchanged = true };
   

2. Pass the options to the solve that loads the data. Use Project.Solve with your ProjectData for a long-lived project, or Engine.Schedule for a one-shot job.

3. Read every entry of result.Updates. Each Mutation has StartDate, EndDate and Duration set.

The full example below schedules three tasks. review doesn't move, but it's still reported:

using Plen;

var jan1 = Moment.FromYmdHm(2026, 1, 1, 0, 0) ?? throw new InvalidOperationException("invalid date");
var jan5 = Moment.FromYmdHm(2026, 1, 5, 0, 0) ?? throw new InvalidOperationException("invalid date");

var data = new ProjectData
{
    Tasks =
    [
        new TaskData("design") { StartDate = jan1, Duration = 2.0 },
        new TaskData("build") { StartDate = jan1, Duration = 1.0 },
        new TaskData("review") { StartDate = jan5, Duration = 1.0 },
    ],
    Links = [new LinkData { Id = "design-build", Source = "design", Target = "build" }],
};
// 24/7 time keeps the example dates easy to check.
data.Config.UseCalendars = false;

var options = new SolveOptions { IncludeUnchanged = true };

var project = new Project();
var result = project.Solve(data, options);

foreach (var m in result.Updates)
{
    Console.WriteLine($"{m.Id} {m.StartDate}..{m.EndDate} {m.Duration}");
}

Get the full list from an already solved project#

To reload every date later, call Solve(null, …) with the same options. On a solved project with no pending edits, the call doesn't replan or change the accepted state, and BaselineId stays the same:

var allDates = project.Solve(null, options);

Switch back to sparse results for the edits that follow. A default SolveOptions returns only what changed:

var next = project.Solve(null, new SolveOptions());

The result cache uses the whole SolveOptions as its key, compared by value. An IncludeUnchanged call never gets a cached sparse result, and a sparse call never gets a cached full one. Repeating a call with equal options returns the same ScheduleResult object, so treat it as read-only, or call DeepClone() before you change it.

What is and isn't reported#

• The result includes every scheduled task: leaf tasks, summaries and milestones. Check Mutation.Kind to tell them apart.
• Tasks with Unscheduled = true are never reported.
• LevelingDelay and Pauses are always null, because a solve doesn't change them.
• BaselineId follows real changes only. Asking for unchanged tasks doesn't create a new baseline.
• With Subtree, the result holds every task in the subtree, including the subtree tasks' ancestors. Tasks outside the subtree appear only when a sparse subtree solve would report them too, because they changed or were edited.
• On a project with a dependency cycle, nothing is scheduled. The result still lists every scheduled task, in model order, with its dates and duration as stored. Subtree is ignored, and no entry has a Reason, even with Reasons = true.
• Project.Preview and Project.Level always return sparse updates.

Result#

The example prints one line per task, including review, which didn't move (the lines may come in a different order):

design 2026-01-01 00:00..2026-01-03 00:00 2
build 2026-01-03 00:00..2026-01-04 00:00 1
review 2026-01-05 00:00..2026-01-06 00:00 1

Without IncludeUnchanged, the same solve reports only build.

See Reading results for how to write the dates back into your model.