private void btnSave_Click(object sender, EventArgs e)
 {
     if (!tbMinQuantityImport.Text.Equals("") && !tbMaxQuantityInventory.Text.Equals(""))
     {
         _business.ChangeStockContracts(Int32.Parse(tbMinQuantityImport.Text), Int32.Parse(tbMaxQuantityInventory.Text));
     }
 }