检查C＃驱动程序从MongoDB投影生成的查询

Question

我使用投影查询mongodb的C＃驱动程序数据。代码如下：

var filter = Builders<User>.Filter.Eq("_id", userId);
var projection = Builders<User>.Projection.Expression(u => Tuple.Create(u.UserId, u.UserName));
var cursor = await collection.Find(filter).Project(projection).ToCursorAsync();

如何检查C＃代码生成的查询？