C# MongoDB complex class serialization

Question

I\'m working with C# MongoDB driver and I have this rather complex JSON struct to save:

{
    \"name\" : \"value\",
    \"age\": 1,
    \"isFemale\": true,
          


        

Answer 1

A simple way for dealing with this issue and not have to create additional properties, is registering a custom serializer.

ComplexTypeSerializer.cs

namespace MyNamespace.MongoDB.Serializers
{
    public class ComplexTypeSerializer : SerializerBase<object>
    {
        public override object Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
        {
            var serializer = BsonSerializer.LookupSerializer(typeof(BsonDocument));
            var document = serializer.Deserialize(context, args);

            var bsonDocument = document.ToBsonDocument();

            var result = BsonExtensionMethods.ToJson(bsonDocument);
            return JsonConvert.DeserializeObject<IDictionary<string, object>>(result);
        }

        public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, object value)
        {
            var jsonDocument = JsonConvert.SerializeObject(value);
            var bsonDocument = BsonSerializer.Deserialize<BsonDocument>(jsonDocument);

            var serializer = BsonSerializer.LookupSerializer(typeof(BsonDocument));
            serializer.Serialize(context, bsonDocument.AsBsonValue);
        }
    }
}

And register it as per http://mongodb.github.io/mongo-csharp-driver/2.3/reference/bson/serialization/

BsonSerializer.RegisterSerializer(typeof(IDictionary<string, object>), new ComplexTypeSerializer());

or

BsonSerializer.RegisterSerializer(typeof(IList<IDictionary<string, object>>), new ComplexTypeSerializer());

The code below was tested with a simple IDictionary<string, object>, not sure if it would work with IList<IDictionary<string, object>>, however if it's not supported, you can create another custom serializer to support it.

Answer 2

Try to read the documentation more carefully, within the Serializer Registry section (http://mongodb.github.io/mongo-csharp-driver/2.4/reference/bson/serialization/#serializer-registry):

The serializer registry contains all the IBsonSerializers that have been registered. It can be accessed via the SerializerRegistry property of the static class BsonSerializer.

To register a serializer use either

BsonSerializer.RegisterSerializer(Type, IBsonSerializer)    

or

BsonSerializer.RegisterSerializer<T>(IBsonSerializer<T>)

This will add them to

BsonSerializer.SerializerRegistry

Checkout the APIs for these classes here - http://mongodb.github.io/mongo-csharp-driver/2.4/apidocs/html/T_MongoDB_Bson_Serialization_BsonSerializer.htm

Answer 3

Found how to save the data to MongoDB here: Dictionary-to-BsonDocument conversion omitting _t field and extended it a bit so I thought to share the full solution.

Step #1:

In my class, I declared 2 members for each value:

// For the Hobbies object type:
[BsonIgnore] //ignore this value in MongoDB
public Dictionary<string, object> Hobbies { get; set; }

[JsonIgnore] //ignore this value in the response on Get requests
[BsonElement(elementName: "Hobbies")]
public BsonDocument HobbiesBson { get; set; }

/*********************************************************************/

// For the Collection object type:
[BsonIgnore] //ignore this value in MongoDB
public List<Dictionary<string, object>> Collection { get; set; }

[JsonIgnore] //ignore this value in the response on Get requests
[BsonElement(elementName: "Collection")]
public BsonArray CollectionBson { get; set; }

Step #2

In my WebAPI controller method for Post

[HttpPost]
public override async Task<IActionResult> Post([FromBody] Person person)
{
    var jsonDoc = JsonConvert.SerializeObject(person.Hobbies);
    person.HobbiesBson = BsonSerializer.Deserialize<BsonDocument>(jsonDoc);

    jsonDoc = JsonConvert.SerializeObject(person.Collection);
    person.CollectionBson = BsonSerializer.Deserialize<BsonArray>(jsonDoc);

    //save
}

Step #3

In my Get request I deserialize it back like this:

[HttpGet("{id?}")]
public override async Task<IActionResult> Get(string id = null)
{
    var people = //get data from mongoDB
    foreach (var person in people)
    {
        var bsonDoc = BsonExtensionMethods.ToJson(person.HobbiesBson);
        person.Hobbies = JsonConvert.DeserializeObject<Dictionary<string, object>>(bsonDoc);

        bsonDoc = BsonExtensionMethods.ToJson(person.CollectionBson);
        person.Collection = JsonConvert.DeserializeObject<List<Dictionary<string, object>>>(bsonDoc);bsonDoc);
    }
    return Ok(people);
}

This solved my issue and I hope it can help others as well :-)