Serializing object graph using MongoDB Bson serializer - serialization

Question

I've been playing a little with the MongoDB Bson serializer, using the following piece of code:
class Program
{
public class myValue
{
public int Id = 0;
public string Label = "";
}
public class myValueMap : Dictionary<string, myValue>
{
}
public class myProdData
{
public myValueMap Mapping { get; set; }
}
public class mySystemPosition
{
public string Text { get; set; }
public myProdData ProdData { get; set; }
}
static void Main(string[] args)
{
BsonClassMap.RegisterClassMap<mySystemPosition>();
BsonClassMap.RegisterClassMap<myProdData>();
BsonClassMap.RegisterClassMap<myValueMap>();
BsonClassMap.RegisterClassMap<myValue>();
var o = new mySystemPosition()
{
ProdData = new myProdData()
{
Mapping = new myValueMap()
{
{"123", new myValue() {Id = 1, Label = "Item1"}},
{"345", new myValue() {Id = 2, Label = "Item2"}},
}
}
};
var bson = o.ToBson();
var text = Encoding.ASCII.GetString(bson);
}
}
however I don't seem to be able to get the myProdData.Mapping serialized....
Do I need to configure the MongoDB Bson serializer in a special way, to make this work?

Answer 1

You no need to use BsonClassMap.RegisterClassMap if you no need custom serializtion(documentation).
All your classes will be desirialzied according to default rules.
Also i am changed your example a little bit to get it work(i've replaces myValueMap class with Dictionary):
public class myProdData
{
public Dictionary<string, myValue> Mapping { get; set; }
}
static void Main(string[] args)
{
var o = new mySystemPosition()
{
ProdData = new myProdData()
{
Mapping = new Dictionary<string, myValue>()
{
{"123", new myValue() {Id = 1, Label = "Item1"}},
{"345", new myValue() {Id = 2, Label = "Item2"}},
}
}
};
var json = o.ToJson();
Console.WriteLine(json);
Console.ReadKey();
}
Here is console output(just well formatted):
{
"Text":null,
"ProdData":{
"Mapping":{
"123":{
"_id":1,
"Label":"Item1"
},
"345":{
"_id":2,
"Label":"Item2"
}
}
}
}
You can test your serializtion using ToJson() extention method, in order to view that all correct and after that use ToBson() if need.

Answer 2

The problem is that myValueMap derives from Dictionary. That results in a class that the AutoMap method can't handle.
I recommend you just use the Dictionary directly, as Andrew did in his reply.

Answer 3

Ufortunately the myValueMap is an object that I can't easily change, however it turns out, that's pretty easy to create your own (de)serializer....
public class myValueMapSerializer : IBsonSerializer
{
public object Deserialize(Bson.IO.BsonReader bsonReader, System.Type nominalType, System.Type actualType, IBsonSerializationOptions options)
{
if (nominalType != typeof(myValueMap)) throw new ArgumentException("Cannot serialize anything but myValueMap");
var res = new myValueMap();
var ser = new DictionarySerializer<string, myValue>();
var dic = (Dictionary<string, myValue>)ser.Deserialize(bsonReader, typeof(Dictionary<string, myValue>), options);
foreach (var item in dic)
{
res.Add(item.Key, item.Value);
}
return res;
}
public object Deserialize(Bson.IO.BsonReader bsonReader, System.Type nominalType, IBsonSerializationOptions options)
{
throw new Exception("Not implemented");
}
public bool GetDocumentId(object document, out object id, out IIdGenerator idGenerator)
{
id = null;
idGenerator = null;
return false;
}
public void Serialize(Bson.IO.BsonWriter bsonWriter, Type nominalType, object value, IBsonSerializationOptions options)
{
if (nominalType != typeof(myValueMap)) throw new ArgumentException("Cannot serialize anything but myValueMap");
var ser = new DictionarySerializer<string, myValue>();
ser.Serialize(bsonWriter, typeof(DictionarySerializer<string, myValue>), value, options);
}
public void SetDocumentId(object document, object id)
{
return;
}
}