public static Task<int> CountColumnAsync<TSource, TColumnType>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, TColumnType>> selector,
	bool applyDistinct,
	CancellationToken cancellationToken
)

<ExtensionAttribute>
Public Shared Function CountColumnAsync(Of TSource, TColumnType) ( 
	source As IQueryable(Of TSource),
	selector As Expression(Of Func(Of TSource, TColumnType)),
	applyDistinct As Boolean,
	cancellationToken As CancellationToken
) As Task(Of Integer)