将复杂类添加到Mongo

我在尝试将复杂类型添加到Mongo中的现有文档时遇到了麻烦.

我有以下两个班级.

public class UserObjectCollection {

    [BsonId]
    public Guid UserId { get; set; }

    public Dictionary UserObjects { get; set; }

    public UserObjectCollection() {
        UserObjects = new Dictionary();
    }
}

public class ComplexClass {
    public string Bar { get; set; }
    public int Foo { get; set; }
}

然后我创建一个新的插入对象.

var bd = new UserObjectCollection() {
    UserId = Guid.NewGuid(),
    UserObjects = {
        { "data", 12 },
        { "data2", 123 },
        { "data3", new ComplexClass() { Bar= "bar", Foo=1234 } }
    }
};

插入文档.

mongoCollection.Insert(bd.ToBsonDocument());

我得到了结果文件.

{"_ id":BinData(3,"t089M1E1j0OFVS3YVuEDwg =="),"UserObjects":{"data":12,"data2":123,"data3":{"_ t":"ComplexClass","Bar": "bar","Foo":1234}}}

文档正确插入.然后我修改其中一个值.

var query = Query.EQ("UserObjects.data", BsonValue.Create(12));

collection.FindAndModify(
  query, 
  SortBy.Null, 
  Update.SetWrapped("data2", new ComplexClass() { Foo = -1234, Bar = "FooBar" }),
  returnNew: false, 
  upsert: true);

出现在数据库中的文档.

{"UserObjects":{"data":12,"data2":{"Bar":"FooBar","Foo": - 1234},"data3":{"_ t":"ComplexClass","Bar": "bar","Foo":1234}},"_ id":BinData(3,"W11Jy + hYqE2nVfrBdxn54g ==")}

如果我尝试检索此记录,则会收到FileFormatException.

var theDocument = collection.Find(query).First();

(未处理的异常:System.IO.FileFormatException:无法确定反序列化的实际对象.NominalType是System.Object,BsonType是Docum ent.).

与data3不同,data2没有鉴别器.我在做什么？