var client = new MongoClient("mongodb://localhost:27017");
var database = client.GetDatabase("db221");
database.DropCollection("Orders");

var collection = database.GetCollection<Order>("Orders");
collection.InsertMany(
[
    new Order { Id = 1, Foo = 1 },
    new Order { Id = 2, Foo = 1 }
]);

var results = collection.AsQueryable().Where(o => o.Foo < Random.Shared.Next()).ToList();
foreach (var result in results)
{
    Console.WriteLine($"{result.Id} {result.Foo}");
}

public class Order
{
    public int Id { get; set; }
    public int Foo { get; set; }
}