'宣言 Public MustOverride Function Sum( _ ByVal value1 As T, _ ByVal value2 As Nullable(Of Decimal) _ ) As Nullable(Of Decimal)
public abstract Nullable<decimal> Sum( T value1, Nullable<decimal> value2 )
AverageAggregator<T> クラス AverageAggregator<T> メンバ