public static Task<IAsyncCursor<TField>> DistinctAsync<TDocument, TField>(
	this IMongoCollection<TDocument> collection,
	Expression<Func<TDocument, TField>> field,
	Expression<Func<TDocument, bool>> filter,
	DistinctOptions options = null,
	CancellationToken cancellationToken = null
)

<ExtensionAttribute>
Public Shared Function DistinctAsync(Of TDocument, TField) ( 
	collection As IMongoCollection(Of TDocument),
	field As Expression(Of Func(Of TDocument, TField)),
	filter As Expression(Of Func(Of TDocument, Boolean)),
	Optional options As DistinctOptions = Nothing,
	Optional cancellationToken As CancellationToken = Nothing
) As Task(Of IAsyncCursor(Of TField))

[<ExtensionAttribute>]
static member DistinctAsync : 
        collection : IMongoCollection<'TDocument> * 
        field : Expression<Func<'TDocument, 'TField>> * 
        filter : Expression<Func<'TDocument, bool>> * 
        ?options : DistinctOptions * 
        ?cancellationToken : CancellationToken 
(* Defaults:
        let _options = defaultArg options null
        let _cancellationToken = defaultArg cancellationToken null
*)
-> Task<IAsyncCursor<'TField>>