Code:

using System.Data.OleDb;

    public partial class Form1 : Form
    {
        private void btnUlogujSe_Click(object sender, EventArgs e)
        {
            GlPod.cn = GlMetode.KreirajKonekciju(txtKorisnickoIme.Text, txtLozinka.Text);
            OleDbCommand cmd = new OleDbCommand("SELECT Naziv FROM Sifarnik", GlPod.cn);
            DataTable dt = new DataTable("dt");
            dt.Columns.Add(new DataColumn("Naziv", Type.GetType("System.String")));
            try
            {
                GlPod.cn.Open();
                dt.Load(cmd.ExecuteReader());
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                txtKorisnickoIme.SelectAll();
                txtKorisnickoIme.Focus();
            }
            finally
            {
                GlPod.cn.Close();
            }
        }
    }


    public static class GlMetode
    {
        public static OleDbConnection KreirajKonekciju(string KorisnickoIme, string Lozinka)
        {
            OleDbConnection OdbcConn = new OleDbConnection("Provider=Microsoft.JET.OLEDB.4.0;data source=" + GlPod.DataSourceFileName + 
                "; JET OLEDB:Engine type = 5; JET OLEDB:System database = " + GlPod.SystemDatabaseFileName +
                "; User id = " + KorisnickoIme + "; Password = " + Lozinka + ";");
            return OdbcConn;
        }
    }