C# MongoDB - How to add and remove item to multiple nested array elements?

Question

I have a document in MongoDB that looks like that:

{
    "Id":"123",
    "Product": "test",
    "Tags":[
        {
            "Name": "name",
            "Categories": [
                {
                    //item
                },
                {
                    //item
                }
            ]
        },
        {
            "Name": "name",
            "Categories": [
                {
                    //item
                },
                {
                    //item
                }
            ]
        }
    ]
}

Now, I need to add a new Item and it needs to be added to all of the categories of the Tags element of that Product by its Id . For example, when I'll insert Item 3 the document should look like this:

{
    "Id":"123",
    "Product": "test",
    "Tags":[
        {
            "Name": "name",
            "Categories": [
                {
                    //item 1
                },
                {
                    //item 2
                },
                {
                    //item 3
                }
            ]
        },
        {
            "Name": "name",
            "Categories": [
                {
                    //item 1
                },
                {
                    //item 2
                },
                {
                    //item 3
                }
            ]
        }
    ]
}

and same goes for removing an item, it needs to be removed from all of the categories as well. Is there a way to do that with the C# MongoDB Driver without pulling the object and "manually" updating them?

Answer 1

You can try something like below in 2.5 driver with 3.6 version.

Finds the document with filter criteria and update which includes new positional identifier to update multiple elements in array inside UpdateOne method.

$[] updates all the Tags arrays to include new item in all Categories array. It acts as a placeholder for updating all elements in array.

Push

var filter = Builders<Product>.Filter.Eq("Id", "123");
var update = Builders<Product>.Update.Push("Tags.$[].Categories", "Item 3");
var result = collection.UpdateOne(filter, update);

Pull

var filter = Builders<Product>.Filter.Eq("Id", "123");
var update = Builders<Product>.Update.Pull("Tags.$[].Categories", "Item 3");
var result = collection.UpdateOne(filter, update);

Additional Information:

You can set the ArrayFilters options in UpdateOptions for applying query criteria on nested array to control what elements to update.

For example to update all the Categories in Tags array where each tag has Name name.

var filter = Builders<Product>.Filter.Eq("Id", "123");
var update = Builders<Product>.Update.Push("Tags.$[t].Categories", "Item 3");
var arrayFilters = new List<ArrayFilterDefinition>{ new ArrayFilterDefinition(new BsonDocument("t.Name", "name")) };
var updateOptions = new UpdateOptions({ArrayFilters = arrayFilters});
var result = collection.UpdateOne(filter, update, updateOptions);