Populate data in Combo Box

public void PopulateGCSCompany(ListBox list, String connectionString)
        {
            StringBuilder sbQuery = new StringBuilder();

            sbQuery.AppendLine(" SELECT ");
            sbQuery.AppendLine(" [GCSCompanyId],[CompanyName] ");
            sbQuery.AppendLine("  FROM [GCSCompany] ");
            sbQuery.AppendLine(" ORDER BY [CompanyName] ASC ");

            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                DataTable companyDataTable = new DataTable();
                SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(sbQuery.ToString(), conn);
                sqlDataAdapter.Fill(companyDataTable);

                list.DataValueField = "GCSCompanyId";
                list.DataTextField = "CompanyName";
                list.DataSource = companyDataTable;
                list.DataBind();

                list.Items.Insert(0, new ListItem("", "0"));
            }
        }