Is there a straight forward way to update nested array of entities in MongoDB. I am using MongoDB C# Driver
for making the DB call from application. Below is an exmaple : say I have a Student
collection where each document has a nested array of Course
with some necessary fields populated and Course
by itself is a separate collection like:
{
"_id": "234dssfcv456",
"Name": "Jean Douglas",
"Age": 32,
"Courses":
[
{
"_id": "1234",
"Name": "Computer Science",
"Level": "Basic"
},
{
"_id": "3456",
"Name": "Bio Science",
"Level": "Intermediate"
}
]
}
I know I can update the nested entity by index something like below but I don't know the index and rather know only the nested Course
object Id
only.
db.College.Student.update(
{"Student._id": "234dssfcv456"},
{$set: {
"Student.$.Courses.1.Level": "Basic"
}}
Right now, am reading the entire nested array of courses -> doing the modification at application end -> then passing the entire array for update with the filedname "Courses"
which is going to replace the existing array with the one passed.
But was thinking, is there an way I can update one entity in array with the Id
available. Please suggest.
*** On the right side in Related question section all shows updating the nested array of objects using the index of the object item which is not a possibility for me.
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 schema:
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; }
}
Lookup Mongo docs for the positional operator. With driver higher than version 2.2.3.3 I am using:
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);