使用MS访问的C#连接不起作用

当我开始调试并添加一些客户端时，我可以添加、更新和读取它们。但是新添加的客户端不会保存在我的数据库中。我已经检查了我是否使用了正确的文件位置，我是：

public class DBaccess
{
    private static string connectionstr;
    static DBaccess()
    {
        string mdffile;
        mdffile = @"C:'Users'rik'Documents'Visual Studio 2010'Projects'Week-2-Opdracht'Database'Clienten.accdb";
        connectionstr = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + mdffile + ";";
    }
    public static DataSet Getwaardenquery(string sqlstr)
    {
        DataSet ds = new DataSet();
        Console.WriteLine(sqlstr);
        OleDbConnection con = new OleDbConnection(connectionstr);
        OleDbDataAdapter dap = new OleDbDataAdapter(sqlstr, con);
        dap.Fill(ds);
        return ds;
    }
    public static int Uitvoerenquery(string sqlstr)
    {
        int resultaat = -1;
        Console.WriteLine(sqlstr);
        OleDbConnection con = new OleDbConnection(connectionstr);
        OleDbCommand cmd = new OleDbCommand(sqlstr, con);
        try
        {
            con.Open();
            resultaat = cmd.ExecuteNonQuery();
        }
        catch (Exception exp)
        {
            string x = exp.Message;
        }
        finally
        {
            if (con.State == ConnectionState.Open)
            {
                con.Close();
            }
        }
        return resultaat;
    }
}
}