Update field inside the list using MongoDB C# driver

Question

I have multiple MongoDB documents like this:

{
    "_id":"abcde",
    "Students":[
        {"Name":"John","IsNew":true},
        {"Name":"Steve","IsNew":true}
    ],
}

{
    "_id":"fghij",
    "Students":[
        {"Name":"Ron","IsNew":true},
        {"Name":"Mike","IsNew":true}
    ],
}

How to update the IsNew field to false for all students for every document using C# driver?

Can you show what you have tried?

cl0ud
– cl0ud

2019-02-04 11:35:42 +00:00
Commented Feb 4, 2019 at 11:35 — cl0ud
– cl0ud, Commented Feb 4, 2019 at 11:35

mickl · Accepted Answer · 2019-02-05 17:34:00Z

3

You can use UpdateMany method from MongoDB C# driver with the positional all operator:

var filter = Builders<YourModel>.Filter.Exists(x => x.Students);

FieldDefinition<YourModel, bool> field = "Students.$[].IsNew";
var update = Builders<YourModel>.Update.Set(field, false);

Col.UpdateMany(filter, update);

EDIT: you can use .Exists() as a filter to make sure that Students array is present in all the documents that are being updated

edited Feb 5, 2019 at 17:34

answered Feb 4, 2019 at 16:16

mickl

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4 Comments

nff Over a year ago

Thanks for the answer. It worked but students array is not present in all the documents. If students array is not in the document, then compiler throws error: Students must exist in the document.

mickl Over a year ago

@nff modified my answer

nff Over a year ago

Thanks @mickl .Is there any way we can filter the documents such that it only updates the elements having IsNew flag as true?. With the current approach, filter contains all the documents having Students list.

mickl Over a year ago

@nff sorry for the delay, please open new question if you still need help since it significantly changes the scope of current question

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