Is there mongodb C# driver support System.Dynamic.DynamicObject in .NET 4?

Question

Im working on a project that use .NET Razor and mongodb. I would like to do something like this:

@{
    var feeds = DP.Database.GetCollection("feeds").FindAll();
}
<ul>
    @foreach (dynamic feed in feeds)
    {
        <li>@feed.message - @feed.from.name</li>
    }
</ul>

However, the current mongodb C# driver FindAll() return collection of BsonDocument which does not support dynamic object. Anybody know a .NET 4 dynamic supported mongodb C# driver?

Thanks a lot

Answer 1

Currently, there is no support for dynamic in the MongoDB driver. This is because it is based on .NET 3.5. However, since a .NET 4.0 assembly can reference a .NET 3.5 assembly, it is possible for you to write a IBsonSerializationProvider and an IBsonSerializer in .NET 4.0 to support dynamics.

We, 10gen, are looking at doing this in the future. I have spiked some support at https://github.com/craiggwilson/mongo-csharp-driver/tree/dynamic if you want to take a look. There are most definitely bugs, but it shows that it is possible.

Answer 2

I created a straight-forward extension to the MongoDB driver that re-serializes the BSON document using Json.NET and deserializes it as a dynamic. By including the following class, you can simply convert your MongoDB queries to dynamic like this

dynamic obj = collection.FindOneByIdAs<BsonDocument>(someObjectId).ToDynamic();

Extension class:

public static class MongoDynamic
{
    private static System.Text.RegularExpressions.Regex objectIdReplace = new System.Text.RegularExpressions.Regex(@"ObjectId\((.[a-f0-9]{24}.)\)", System.Text.RegularExpressions.RegexOptions.Compiled);
    /// <summary>
    /// deserializes this bson doc to a .net dynamic object
    /// </summary>
    /// <param name="bson">bson doc to convert to dynamic</param>
    public static dynamic ToDynamic(this BsonDocument bson)
    {
        var json = objectIdReplace.Replace(bson.ToJson(), (s) => s.Groups[1].Value);
        return Newtonsoft.Json.JsonConvert.DeserializeObject<dynamic>(json);
    }
}

Be sure to reference Newtonsoft.Json.dll (http://james.newtonking.com/projects/json-net.aspx)

Answer 3

I have a clean solution using custom IBsonSerializer and Newtonsoft.Json.

Setup your custom serializer on the BsonClassMap

map.MapProperty(member => member.Data)
   .SetElementName("Data")
   .SetSerializer(new DynamicSerializer());

or on the property

[BsonSerializer(typeof(DynamicSerializer))]
public dynamic Data { get; set; }

And just include the following class

public class DynamicSerializer : IBsonSerializer
{
  #region Implementation of IBsonSerializer

  public object Deserialize(BsonReader bsonReader, Type nominalType, IBsonSerializationOptions options)
  {
    return Deserialize(bsonReader, nominalType, null, options);
  }

  public object Deserialize(BsonReader bsonReader, Type nominalType, Type actualType,
    IBsonSerializationOptions options)
  {
    if (bsonReader.GetCurrentBsonType() != BsonType.Document) throw new Exception("Not document");
    var bsonDocument = BsonSerializer.Deserialize(bsonReader, typeof(BsonDocument), options) as BsonDocument;
    return JsonConvert.DeserializeObject<dynamic>(bsonDocument.ToJson());
  }

  public IBsonSerializationOptions GetDefaultSerializationOptions()
  {
    return new DocumentSerializationOptions();
  }

  public void Serialize(BsonWriter bsonWriter, Type nominalType, object value, IBsonSerializationOptions options)
  {
    var json = (value == null) ? "{}": JsonConvert.SerializeObject(value);
    BsonDocument document = BsonDocument.Parse(json);
    BsonSerializer.Serialize(bsonWriter, typeof(BsonDocument), document,options); 
  }

  #endregion
}

InfoSlips - GlobalKinetic

Answer 4

Just to build on Maximilian's answer. This will return a list of dynamics from any query.

    /// <summary>
    /// deserializes this BsonDocument cursor result to a list of .net dynamic objects
    /// </summary>
    /// <param name="cursor">cursor result to convert to dynamic</param>
    /// <returns></returns>
    public static List<dynamic> ToDynamicList(this MongoCursor<BsonDocument> cursor)
    {
        var dynamicList = new List<dynamic>();
        var list = cursor.ToList();
        for (int i = 0, l = list.Count; i < l; i++)
            dynamicList.Add(list[i].ToDynamic());

        return dynamicList;
    }

Answer 5

Even though this is an old topic its still just as relevant today as when post was made, and I have yet to see any solutions out there that provides a simple solution for two way support, I have modified @Maximilian Scherer code so that it lets you convert to dynamic objects which easily let you save your Document again.

public static class MongoDynamic
{
    /// <summary>
    /// deserializes this bson doc to a .net dynamic object
    /// </summary>
    /// <param name="bson">bson doc to convert to dynamic</param>
    public static dynamic ToDynamic(this BsonDocument bson)
    {
        var json = bson.ToJson(new MongoDB.Bson.IO.JsonWriterSettings { OutputMode = JsonOutputMode.Strict });
        dynamic e =  Newtonsoft.Json.JsonConvert.DeserializeObject<ExpandoObject>(json);
        BsonValue id;
        if (bson.TryGetValue("_id", out id))
        {
            // Lets set _id again so that its possible to save document.
            e._id = new ObjectId(id.ToString());
        }
        return e;
    }
}

Example of usage:

// Get BsonDocument from db here
BsonDocument doc = ...

// Convert to dynamic.
var d = doc.ToDynamic();

// Lets add a none existant property.
d.Name = "test";

// Assuming you already have your collection set up
collection.Save(new BsonDocument(d));