fetch data in combobox in windows form

private void vfind_SelectedIndexChanged(object sender, EventArgs e)
        {
            Vbtnsave.Visible = false;
         
                SqlDataAdapter da = new SqlDataAdapter("select * from VisitorPass where PassNo ='" + vfind.SelectedValue.ToString() + "'", objConn1);
                DataSet ds = new DataSet();
                da.Fill(ds, "VisitorPass");
                if (ds.Tables["VisitorPass"].Rows.Count > 0)
                {
                    MainCombo.SelectedValue = ds.Tables["VisitorPass"].Rows[0]["PassType"].ToString();
                    txtvpassno.Text = ds.Tables["VisitorPass"].Rows[0]["PassNo"].ToString();
                    VdateTimePicker1.Value = Convert.ToDateTime(ds.Tables["VisitorPass"].Rows[0]["Date"].ToString());
                    Dttimein.Value = Convert.ToDateTime(ds.Tables["VisitorPass"].Rows[0]["Timein"].ToString());
                    Dttimeout.Value = Convert.ToDateTime(ds.Tables["VisitorPass"].Rows[0]["Timeout"].ToString());
                    txtvpassno.Text = ds.Tables["VisitorPass"].Rows[0]["VisitorsName"].ToString();
                    txtvpassno.Text = ds.Tables["VisitorPass"].Rows[0]["Purpose"].ToString();
                    txtvpassno.Text = ds.Tables["VisitorPass"].Rows[0]["ToSee"].ToString();
                    vauthcombo.SelectedValue = ds.Tables["VisitorPass"].Rows[0]["AuthorisedSign"].ToString();

                
            }
        }