public static decimal GetTotal(
Func<DateTime, DateTime, HierarchyId, HierarchyId, decimal> totalFunc,
DateTime startDate,
DateTime endDate,
HierarchyId activityNode,
HierarchyId centreNode,
HierarchyId[] nodes)
{
return activityNode == null
? nodes.Sum(a => totalFunc(startDate, endDate, a, centreNode))
: totalFunc(startDate, endDate, activityNode, centreNode);
}