public static IMongoQueryable<TResult> GroupBy<TSource, TKey, TResult>(
	this IMongoQueryable<TSource> source,
	Expression<Func<TSource, TKey>> keySelector,
	Expression<Func<TKey, IEnumerable<TSource>, TResult>> resultSelector
)

<ExtensionAttribute>
Public Shared Function GroupBy(Of TSource, TKey, TResult) ( 
	source As IMongoQueryable(Of TSource),
	keySelector As Expression(Of Func(Of TSource, TKey)),
	resultSelector As Expression(Of Func(Of TKey, IEnumerable(Of TSource), TResult))
) As IMongoQueryable(Of TResult)

[<ExtensionAttribute>]
static member GroupBy : 
        source : IMongoQueryable<'TSource> * 
        keySelector : Expression<Func<'TSource, 'TKey>> * 
        resultSelector : Expression<Func<'TKey, IEnumerable<'TSource>, 'TResult>> -> IMongoQueryable<'TResult>