Insert Dictionary into MongoDB with c# driver

Question

I am in a situation where I can't predict which fields my MongoDB document is going to have. So I can no longer create an object with an _id field of type BsonID. I find it very convenient to create a Dictionary (HashTable) and add my DateTime and String objects inside, as many times as I need it.

I then try to insert the resulting Dictionary object into MongoDb, but default serialization fails.

Here's my object of Type HashTable (like a Dictionary, but with varied types inside):

{ "_id":"",
"metadata1":"asaad",
"metadata2":[],
"metadata3":ISODate("somedatehere")}

And the error from the driver I get is:

Serializer DictionarySerializer expected serialization options of type DictionarySerializationOptions, not DocumentSerializationOptions

I googled it, but couldn't find anything useful. What am I doing wrong?

Robert Stam · Accepted Answer · 2013-05-08 21:09:35Z

24

The driver needs to be able to find the _id field. You could create a C# class that has just two properties: Id and Values.

public class HashTableDocument
{
    public ObjectId Id { get; set; }
    [BsonExtraElements]
    public Dictionary<string, object> Values { get; set; }

}

Note that we have to use Dictionary<string, object> instead of Hashtable.

You could then use code like the following to insert a document:

var document = new HashTableDocument
{
    Id = ObjectId.GenerateNewId(),
    Values = new Dictionary<string, object>
    {
        { "metadata1", "asaad" },
        { "metadata2", new object[0] },
        { "metadata3", DateTime.UtcNow }
    }
};
collection.Insert(document);

We can use the MongoDB shell to confirm that the inserted document has the desired form:

> db.test.find().pretty()
{
        "_id" : ObjectId("518abdd4e447ad1f78f74fb1"),
        "metadata1" : "asaad",
        "metadata2" : [ ],
        "metadata3" : ISODate("2013-05-08T21:04:20.895Z")
}
>

answered May 8, 2013 at 21:09

Robert Stam

12.2k2 gold badges41 silver badges36 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Jeb50 Over a year ago

@RobertStam This provides solution for "dynamic" fields. Two questioins: 1) in a bakery app, users prefer to keep their own convention of writing brand A, sugar, 2 (implies spoon), 300 (implies temperature), 20 (implies minutes). Each doesn't have a key. 2) As I do more reading, mapping class also points out I have to use IDictionary, Fine. But it states it won't preserve the order. Any way to preserve order?

Collectives™ on Stack Overflow

Insert Dictionary into MongoDB with c# driver

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related