C# mongodb - how to update nested array elements

Question

I have the following JSON structure that represents an item

{
    Id: "a",
    Array1: [{
        Id: "b",
        Array2: [{
            Id: "c",
            Array3: [
                {...}
            ]
        }]
    }]
}

I need to be able to either replace the array element in Array2 with a new item or to replace just Array3 with a new array.

Here is my code to replace the array item in Array2:

await Collection.UpdateOneAsync(
    item => item.Id.Equals("a") &&
    item.Array1.Any(a => a.Id.Equals("b")) &&
    item.Array1[-1].Array2.Any(b => b.Id.Equals("c")),
    Builders<Item>.Update.Set(s => s.Array1[-1].Array2[-1], newArray2Item)
);

When executing this code I'm getting this error:

"A write operation resulted in an error.
 Too many positional (i.e. '$') elements found in path 'Array1.$.Array2.$'"

Here is my code to replace Array3 within Array2:

await Collection.UpdateOneAsync(
        item => item.Id.Equals("a") &&
        item.Array1.Any(a => a.Id.Equals("b")) &&
        item.Array1[-1].Array2.Any(b => b.Id.Equals("c")),
        Builders<Item>.Update.Set(s => s.Array1[-1].Array2[-1].Array3, newArray3)
    );

And this is the error:

"A write operation resulted in an error.
 Too many positional (i.e. '$') elements found in path 'Array1.$.Array2.$.Array3'"

I'm using C# MongoDB driver version 2.5.0 and MongoDB version 3.6.1

I found this Jira ticket Positional Operator Matching Nested Arrays that says the problem was fixed and they suggested this syntax for the update

Update all matching documents in nested array:

db.coll.update({}, {$set: {“a.$[i].c.$[j].d”: 2}}, {arrayFilters: [{“i.b”: 0}, {“j.d”: 0}]})
Input: {a: [{b: 0, c: [{d: 0}, {d: 1}]}, {b: 1, c: [{d: 0}, {d: 1}]}]}
Output: {a: [{b: 0, c: [{d: 2}, {d: 1}]}, {b: 1, c: [{d: 0}, {d: 1}]}]}

So I converted it to my elements:

db.getCollection('Items').update(
{"Id": "a"},
{$set: {"Array1.$[i].Array2.$[j].Array3": [newArray3]}}, 
{arrayFilters: 
    [
        {"i.Id": "b"}, 
        {"j.Id": "c"}
    ]}
)

And got this error:

cannot use the part (Array1 of Array.$[i].Array2.$[j].Array3) to traverse the element

Any ideas on how to solve this error?

Answer 1

Here's the C# version of what you need:

var filter = Builders<Item>.Filter.Eq("Id", "a");
var update = Builders<Item>.Update.Set("Array1.$[i].Array2.$[j].Array3", new[] { new Item { Id = "d" } });
var arrayFilters = new List<ArrayFilterDefinition> { new JsonArrayFilterDefinition<Item>("{'i.Id': 'b'}"), new JsonArrayFilterDefinition<Item>("{'j.Id': 'c'}") };
var updateOptions = new UpdateOptions { ArrayFilters = arrayFilters };
collection.UpdateOne(filter, update, updateOptions);