C# mongodb - how to update nested array elements - mongodb

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);