Convert MongoDB BsonDocument to valid JSON in C#

Question

I am working with the MongoDB C# driver. I have a BsonDocument with some data which includes some MongoDB-specific types (like ObjectIDs and ISODates). I want t

Answer 1

MongoDB.Bson (2.5+) has support to map between BsonValues and .Net objects. BsonTypeMapper Class

To map a BsonValue (or BsonDocument) to .Net object use

var dotNetObj = BsonTypeMapper.MapToDotNetValue(bsonDoc);

You can then use your choice of serialization library. For example,

JsonConvert.SerializeObject(dotNetObj);

If you have a List of BsonDocument

var dotNetObjList = bsonDocList.ConvertAll(BsonTypeMapper.MapToDotNetValue);

Answer 2

If the contents of the BSON document is saved as, below

{
"Date" : "2019-04-05T07:07:31.979Z",
"BSONCONTENT" : {
    "_t" : "MongoDB.Bson.BsonDocument, MongoDB.Bson",
    "_v" : {
        "A" : "XXXX",
        "B" : 234   
           }  
 }     

}

then it works with generic class.

private static T ProcessBsonConversion<T>(BsonDocument data)
    {
        var content = data.GetElement("_v");
        var jsonDataContent= content.Value.AsBsonValue.ToJson();
        return Newtonsoft.Json.JsonConvert.DeserializeObject<T>(jsonDataContent);

    }

Answer 3

Most of the Time for this I use, Json.NET

JsonConvert.SerializeObject(obj); 

Most of the time that does the trick. If need be you can set some JsonSerializerSettings

Answer 4

In my opinion the best option is to use Newtonsoft.Json.Bson.BsonReader. Here a complete example:

public string ToJson(BsonDocument bson)
{
    using (var stream = new MemoryStream())
    {
        using (var writer = new BsonBinaryWriter(stream))
        {
            BsonSerializer.Serialize(writer, typeof(BsonDocument), bson);
        }
        stream.Seek(0, SeekOrigin.Begin);
        using (var reader = new Newtonsoft.Json.Bson.BsonReader(stream))
        {
            var sb = new StringBuilder();
            var sw = new StringWriter(sb);
            using (var jWriter = new JsonTextWriter(sw))
            {
                jWriter.DateTimeZoneHandling = DateTimeZoneHandling.Utc;
                jWriter.WriteToken(reader);
            }
            return sb.ToString();
        }
    }
}

I think that this should handle all cases correctly (dates, ids, ...).