gistfile1.txt

public  IEnumerable<T> MapReduce(Expression<Func<T, bool>> predicate,string mapString,string reduceString)
{
    var query = ((MongoQueryable<T>)this.collection.AsQueryable<T>().Where(predicate)).GetMongoQuery();
    var mrResult = this.collection.MapReduce(query, new BsonJavaScript(mapString), new BsonJavaScript(reduceString));
    return  mrResult.GetInlineResultsAs<T>();
}