Есть NoRM для MongoDB Вот пример с их сайта:
public Post GetMostRecentPost()
{
Post mostRecentPost;
using(var db = Mongo.Create("mongodb://localhost/BlogApp"))
{
var posts = db.GetCollection<Post>();
//create a LINQ queryable to search the DB.
var q = posts.AsQueryable();
//the ordering happens on the server and only one result will be returned.
mostRecentPost = q.OrderByDescending(y=>y.PostDate).FirstOrDefault();
}
return mostRecentPost;
}