public abstract Task<long> CountAsync(
	FilterDefinition<TDocument> filter,
	CountOptions options = null,
	CancellationToken cancellationToken = null
)

Public MustOverride Function CountAsync ( 
	filter As FilterDefinition(Of TDocument),
	Optional options As CountOptions = Nothing,
	Optional cancellationToken As CancellationToken = Nothing
) As Task(Of Long)

abstract CountAsync : 
        filter : FilterDefinition<'TDocument> * 
        ?options : CountOptions * 
        ?cancellationToken : CancellationToken 
(* Defaults:
        let _options = defaultArg options null
        let _cancellationToken = defaultArg cancellationToken null
*)
-> Task<int64>