/// <summary>
/// Add fields to view schedule.
/// </summary>
/// <param name="schedules">List of view schedule.</param>
public void AddFieldToSchedule(Document document, List<ViewSchedule> schedules)
{
    using (Transaction transaction = new Transaction(document, "Adding fields to schedule"))
    {
        transaction.Start();

        foreach (ViewSchedule vs in schedules)
        {
           //Get all schedulable fields from view schedule definition.
           IList<SchedulableField> schedulableFields = vs.Definition.GetSchedulableFields();

           foreach (SchedulableField sf in schedulableFields)
           {
               bool fieldAlreadyAdded = false;
               //Get all schedule field ids
               IList<ScheduleFieldId> ids = vs.Definition.GetFieldOrder();
               foreach (ScheduleFieldId id in ids)
               {
                   // If the GetSchedulableField() method of gotten schedule field returns same
                   // schedulable field, it means the field is already added to the view schedule.
                   if (vs.Definition.GetField(id).GetSchedulableField() == sf)
                   {
                       fieldAlreadyAdded = true;
                       break;
                   }
               }

               //If schedulable field doesn't exist in view schedule, add it.
               if (fieldAlreadyAdded == false)
               {
                   vs.Definition.AddField(sf);
               }
           }
        }

        transaction.Commit();
    }   
}