protected void companyDropDownList_SelectedIndexChanged(object sender, EventArgs e)
{
int companyId = Convert.ToInt32(companyDropDownList.SelectedItem.Value);
itemDropDownList.DataSource = aStockInManager.GetAllItemByCompanyId(companyId);
itemDropDownList.DataValueField = "ItemId";
itemDropDownList.DataTextField = "ItemName";
itemDropDownList.DataBind();
itemDropDownList.Items.Insert(0, new ListItem("Select", "0"));
}