public static IQueryable<TResult> MapReduce<TSource, TMap, TKey, TResult>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, IEnumerable<TMap>>> mapper,
	Expression<Func<TMap, TKey>> keySelector,
	Expression<Func<TKey, IEnumerable<TMap>, TResult>> reducer
)

<ExtensionAttribute> 
Public Shared Function MapReduce(Of TSource, TMap, TKey, TResult) ( 
	source As IQueryable(Of TSource),
	mapper As Expression(Of Func(Of TSource, IEnumerable(Of TMap))),
	keySelector As Expression(Of Func(Of TMap, TKey)),
	reducer As Expression(Of Func(Of TKey, IEnumerable(Of TMap), TResult))
) As IQueryable(Of TResult)

public:
[ExtensionAttribute]
generic<typename TSource, typename TMap, typename TKey, typename TResult>
static IQueryable<TResult>^ MapReduce(
	IQueryable<TSource>^ source, 
	Expression<Func<TSource, IEnumerable<TMap>^>^>^ mapper, 
	Expression<Func<TMap, TKey>^>^ keySelector, 
	Expression<Func<TKey, IEnumerable<TMap>^, TResult>^>^ reducer
)