i solve my problem
ShopDataSetTableAdapters.CompanyTableAdapter ComTa = new ShopDataSetTableAdapters.CompanyTableAdapter();
ComTa.Fill(shopDataSet1.Company);
object newitem = null;
foreach (var item in comboBox1.Items)
{
if ((((System.Data.DataRowView)(item)).Row).ItemArray[1].ToString()=="Nokia")
{
newitem=item;
break;
}
}
comboBox1.SelectedItem = newitem;