How to use System.Data.OleDb (connect to MS Access DB)

I’m trying to connect to a MS Access database. In MS Visual Studio 2010 it works perfectly using System.Data.OleDb, however in Unity it doesn’t. I’ve already copied the System.Data.dll to the Assets\Plugins folder from Unity (C:\Program Files (x86)\Unity\Editor\Data\Mono\lib\mono\unity), however here is no System.Data.OleDb.dll.
Does anyone an idea how to connect to to a database?

Thanks in advance.

How can we connect OleDB using unity 3D