public static TResult CachedExpression<TSource, TResult>(
    this IQueryable<TSource> source,
    Func<IQueryable<TSource>, TResult> f
)

<ExtensionAttribute>
Public Shared Function CachedExpression(Of TSource, TResult)(
    source As IQueryable(Of TSource),
    f As Func(Of IQueryable(Of TSource), TResult)
) As TResult