Any

Any() : bool

Returns a bool indicating if there's any structures at all in the structure-set.

using (var session = Database.BeginSession())
{
    return session.Any<Order>();
}

or

using (var session = Database.BeginSession())
{
    return session.Query<Order>().Any();
}

or when doing single query operation:

return db.UseOnceTo().Query<Order>().Any();

Any(expression) : bool

Returns a bool indication if there's any structures at all in the structure-set, that matches the predicate.

using (var session = Database.BeginSession())
{
    return session.Query<Order>().Any(o => o.TotalAmount >= 1000);
}

or when doing single query operation:

return db.UseOnceTo().Query<Order>().Any(o => o.TotalAmount >= 1000);