Scott Watermasysk

Still Learning to Code

Dynamics and MongoDB Revisited

A couple of months ago I wrote about wiring up C# 4.0 dynamics with MongoDB. At the time, I opened up the MongoDB-CSharp library and modified a bit of the code.

For obvious reasons this was not a good long term solution. In what appeared to be moment of clarity a couple of days ago, I decided to try to use extension methods and add dynamics on top of MongoDB-CSharp.

To the credit of the MongoDB-CSharp team, getting the basic functionality up and running was very simple. However, in the end it turns out that two compiler hacks (extension methods and dynamics) do not make a right. :)

Once in place, the code to use it looks something like this:

using (var m = new Mongo())
    var db = m["mongocsharp"];
    //ext method to get our "special" collection
    var col = db.GetDynoCollection("sample"); 

    //dynamic object to store our data
    dynamic newDoc = new DynoDocument();
    newDoc.title = "Dyno Collections";
    newDoc.slug = "dyno";


    dynamic query = new DynoDocument(); 
    query.slug = "dyno"
    dynamic result = col.FindOne(query);


While it works, it still feels too awkward to be useful IMO. Normally, this I would just delete something like this, but I am trying to let less code die on my machine, so I published it all as a GitHub gist: DynoMongo.

After working on this, I have come to the following conclusions:

  1. MongoDB-CSharp provides adequate flexibility on a schema if I need it in .NET. Mix in Automapper and a helper or two you are all set.
  2. Norm provides more structure if that is a requirementl
  3. Dynamics are really just a parlor trick. If I want the flexibility of a dynamic language, using C# is a mistake.
  4. I should probably try to do something similar in IronRuby, but with all the excellent MongoDB Ruby libraries out there, I am not sure it is even worth the thought.

Anyway, if someone feels this is interesting or useful, feel free to grab the gist, DynoMongo, and run with it.