public static Task<TSource> FirstAsync<TSource>(
	this IQueryable<TSource> source,
	Expression<Func<TSource, bool>> predicate,
	CancellationToken cancellationToken
)

<ExtensionAttribute>
Public Shared Function FirstAsync(Of TSource) ( 
	source As IQueryable(Of TSource),
	predicate As Expression(Of Func(Of TSource, Boolean)),
	cancellationToken As CancellationToken
) As Task(Of TSource)