更新 MongoDB 中嵌套实体数组中的属性

Mongo shell:

> db.students.find( {_id:"234dssfcv456", "Courses._id":"1234"} ).pretty()
> db.students.update( {_id:"234dssfcv456", "Courses._id":"3456"}, { $set: { "Courses.$.Level" : "Updated" } } )

C#Mongo模式:

public class Student {
  [BsonId]
  [BsonRepresentation(BsonType.String)]
  public string Id { get; set; }
  public string Name { get; set; }
  public int Age { get; set; }
  public Course[] Courses { get; set; }
}

public class Course {
  [BsonId]
  [BsonRepresentation(BsonType.String)]
  public string Id { get; set; }
  public string Name { get; set; }
  public string Level { get; set; }
}

查找Mongo文档中的positional operator个.

  var _client = new MongoClient(@"....");
  var _database = _client.GetDatabase("...");
  var _students =  _database.GetCollection<Student>("students");

  var filter = Builders<Student>.Filter;
  var studentIdAndCourseIdFilter = filter.And(
    filter.Eq(x => x.Id, "234dssfcv456"),
    filter.ElemMatch(x => x.Courses, c => c.Id == "1234") );
   // find student with id and course id
   var student = _students.Find(studentIdAndCourseIdFilter).SingleOrDefault();

  // update with positional operator
  var update = Builders<Student>.Update;      
  var courseLevelSetter = update.Set("Courses.$.Level", "Updated Level");
  _students.UpdateOne(studentIdAndCourseIdFilter, courseLevelSetter);