The duration of the task specifies how long the task will take to complete. GanttView uses the DurationUnits property to specify the units and the Duration property to specify the value for units. The DurationUnit property of the Task class takes DurationUnit enumeration as input to set the unit of duration to Minutes, Hours, Days, Weeks, or Months.

Use the below code to set the task duration in the GanttView.

//Set duration unit and duration of a task
Task1.DurationUnits= DurationUnits.Days;
Task1.Duration = 4;