private void Box2_SelectedIndexChanged(object sender, EventArgs e) { DataTable dt = dm.getDataSet().Tables[0]; string value = Box2.GetItemText(Box2.SelectedItem); List <string> cities = new List <string>(); dt.DefaultView.RowFilter = string.Format("[{0}] LIKE '%{1}%'", Box1.SelectedItem, value); showMarkers(cities, value, dt); }