Deserializing a C# Dictionary in MongoDB Returns Null

Question

I have a simple class:

public class Foo
{
    public ObjectId Id { get; set; }
    public Dictionary<string, object> Bar { get; set; }
}

Nothing else, no custom mappings, etc. When I insert it into MongoDB, it works perfectly, but the Bar property is ignored, although, at insertion time, it is not null. I tried adding [BsonDictionaryOptions] and [BsonElement] but these had no effect.

could you check how it behaves when you change object to int? — profesor79, Mar 04 '16 at 15:11
could you provide mongodb server version and .net driver version? — profesor79, Mar 04 '16 at 16:16
I think it has to do with the "object" part of the dictionary. The driver doesn't know how to deserialize it. — Axel Prieto, Mar 04 '16 at 17:30
I endorse what @AxelPrieto said above. It's object as object can have any arbitrary value, serializable and not serializable. Serializer has no way to know what is stored inside. I'll suggest you to use concrete classes or intrinsic types instead. — Saleem, Mar 04 '16 at 20:15
Sorry, but that's not possible. The option to use [BsonExtraElements] is widely known, and it applies to Dictionary. — Ricardo Peres, Mar 04 '16 at 21:01

profesor79 · Answer 1 · 2016-08-19T10:29:09.107

1

for a test purposes I added to class Foo

[BsonDictionaryOptions]
public Dictionary<string, object> Bar = new Dictionary<string, object>() { 
           { "1", new object() }, 
           { "2", new object() } };

when dictionary is empty - the field is empty, but when we are sending data in it - it reflects inserted data.

{
        "_id" : ObjectId("56d9b9e4c875835548bc62de"),
        "Bar" : {
                "1" : {

                },
                "2" : {

                }
        }
}

and when we have:

 public Dictionary<string, string> Bar =
      new Dictionary<string, string>() { { "1", "text" }, { "2", "text" } };

then output is:

"_id" : ObjectId("56d9bb5ac875835548bc62df"), "Bar" : { "1" : "text", "2" : "text" }

edited Aug 19 '16 at 10:29

answered Mar 04 '16 at 16:40

profesor79

9,213
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OK, but my disctionary was not empty. And I think you need to give an option in the [BsonDictionaryOption], I used create document as arrays, – Ricardo Peres Mar 04 '16 at 17:31
I just added the attribute without any option - maybe this is a key? – profesor79 Mar 04 '16 at 17:39

score 1 · Answer 2 · answered Mar 07 '16 at 11:27

1

The problem is solved: I was using a custom serializer inadvertently.

answered Mar 07 '16 at 11:27

Ricardo Peres

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Deserializing a C# Dictionary in MongoDB Returns Null

2 Answers2