Unity is giving a error when i writte my db commadn code

when i write my code for mysql commands the unity give me the following error

Unhandled Exception: Mono.CSharp.InternalErrorException: Assets/Scripts/Board.cs(9,22): AssemblyCSharp.Board —> Mono.CSharp.InternalErrorException: Assets/Scripts/Board.cs(14,40): AssemblyCSharp.Board.conexao —> System.IO.FileNotFoundException: Could not load file or assembly ‘System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ or one of its dependencies.

i’ve already added all the assemblies and i dont know what to do anymore

----------------------------------Edit 08/12/2014 6:33PM---------------------------------------

Board code VVV

using System;
using System.Collections.Generic;
using System.Linq;
using MySql.Data.MySqlClient;

namespace AssemblyCSharp
{
	public class Board
	{
		public Board ()
		{
		}
		static MySqlConnection conexao = new MySqlConnection("Server=localhost;Database=dngu;Uid=user;Pwd='';");
		public string RetornaBoard()
		{

			MySqlCommand comando = new MySqlCommand("Select * from score order by score_Score desc limit 10",Conexao.conexao);
			string texto = "";

			try
			{
				conexao.Open();
				int i = 1;
				MySqlDataReader reader = comando.ExecuteReader();
				while(reader.Read())
				{
					texto +="#"+i+" "+reader.GetString("score_Nome")+" "+reader.GetString("score_Score")+"

";
i++;
}
}
catch(MySqlException erro)
{
}
finally
{
conexao.Close();
}
return texto;
}

	}
}

Conexao Code VVVV

using MySql.Data.MySqlClient;
namespace AssemblyCSharp
{
		public static class Conexao
		{
		public static MySqlConnection conexao = new MySqlConnection ("Server=localhost;Database=dngu;Uid=user;Pwd='';");
		}
}

I’m removing all the assemblies from my projects, and puting the ones that are in my .net framework folder. its kinda working. if i get any results i’ll do a updtate in the post