call stored procedure with mysql

i’ve been trying to call a stored procedure but no matter how it’s says this:

Assets/Scripts/NewChar.cs(293,45): error CS0266: Cannot implicitly convert type System.Data.ParameterDirection to System.Data.ParameterDirection. An explicit conversion exists (are you missing a cast?)

Note that i already added the System.Data.dll in the Assets.
here is the code:

try
    {

        MySqlCommand cmd = con.ExecutarProcedure("PROC_newChar");

        cmd.Parameters.AddWithValue("_cod_menuChar", Global.LocalClient.MenuCharId);
        cmd.Parameters["_cod_menuChar"].Direction = ParameterDirection.Input;

        cmd.Parameters.AddWithValue("_slot", Global.LocalClient.CurrentSlot);
        cmd.Parameters["_slot"].Direction = ParameterDirection.Input;

        cmd.Parameters.AddWithValue("_name", txt.text);
        cmd.Parameters["_name"].Direction = ParameterDirection.Input;

        cmd.Parameters.AddWithValue("_cod_gang", cod_gang);
        cmd.Parameters["_cod_gang"].Direction = ParameterDirection.Input;

        cmd.Parameters.AddWithValue("_cod_classe", cod_classe);
        cmd.Parameters["_cod_classe"].Direction = ParameterDirection.Input;


        cmd.Parameters.AddWithValue("_retorno", MySqlDbType.Int32);
        cmd.Parameters["_retorno"].Direction = ParameterDirection.Output;

        cmd.ExecuteNonQuery();

         retorno = (int)cmd.Parameters["_retorno"].Value;

    }
    catch (MySqlException ex)
    {
        Debug.Log("Error " + ex.Number + " has occurred: " + ex.Message);
        //retorno = 1;
    }

I had the same problem and this worked for me.

First, you must place the dll files in the asset folder.
Second, make sure to copy only the dll files that are bundled with Unity. If you use microsoft’s dll you might run into errors.
Unity’s dlls are located in:
C:\Program Files\Unity\Editor\Data\Mono\lib\mono

after you copy the files do the following:
open Unity and select File->Build Settings->Player Settings
In the Player Settings panel change Api Compatibility level to .NET 2.0