private void ItemForm_Load(object sender, EventArgs e)
 {
     uow = new EfUnitOfWork();
     comboBoxBrand.SelectedIndexChanged -= comboBoxBrand_SelectedIndexChanged;
     UiHelper.LoadBrands(comboBoxBrand);
     comboBoxBrand.SelectedIndexChanged += comboBoxBrand_SelectedIndexChanged;
     UiHelper.LoadAgents(comboBoxAgent);
     UiHelper.LoadConditions(comboBoxCondition);
     UiHelper.LoadLocations(comboBoxLocation);
     UiHelper.LoadItems(dataGridViewItems);
 }
 static UiHelper()
 {
     if (uow == null)
         uow = new EfUnitOfWork();
 }