public override IAssignment InsertAssignment(IAssignment assignment)
        {
            using (var db = new GanttResourcesEntities())
            {
                int rId = int.Parse(assignment.ResourceID.ToString());
                int tId = int.Parse(assignment.TaskID.ToString());
                decimal units = decimal.Parse(assignment.Units.ToString());
                
                var result = new GanttResourceAssignment { ResourceID = rId, TaskID = tId, Units = units };
                db.GanttResourceAssignments.Add(result);
                db.SaveChanges();

                assignment.ID = result.ID;
                assignment.ResourceID = result.ResourceID;
                assignment.TaskID = result.TaskID;
            }
            return assignment;
        }