public static IQueryable<Nullable<double>> AverageAsQuery<TSource>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, Nullable<long>>> selector
)

<ExtensionAttribute> 
Public Shared Function AverageAsQuery(Of TSource) ( 
	source As IQueryable(Of TSource),
	selector As Expression(Of Func(Of TSource, Nullable(Of Long)))
) As IQueryable(Of Nullable(Of Double))

public:
[ExtensionAttribute]
generic<typename TSource>
static IQueryable<Nullable<double>>^ AverageAsQuery(
	IQueryable<TSource>^ source, 
	Expression<Func<TSource, Nullable<long long>>^>^ selector
)