public static AggregationView<Nullable<long>, Nullable<long>> LiveSum(
	this View<Nullable<long>> source
)

<ExtensionAttribute> _
Public Shared Function LiveSum ( _
	source As View(Of Nullable(Of Long)) _
) As AggregationView(Of Nullable(Of Long), Nullable(Of Long))

Return Value

If the source is empty or contains only nulls, the sum value is zero.

It is possible to use standard LINQ query operator Sum instead of LiveSum. Both are "live" in the sense that they are recomputed automatically when any change occurs in the source. The difference is that Sum will every time loop through the entire source collection and aggregate it from scratch, whereas LiveSum will use a more performant algorithm, will maintain its value incrementally, processing only those source items that actually changed.