C#中后台申明全局变量来判断某一特定值的代码

i f (CheckData())
        {
            return;
        }
 Boolean flag = false;
        if (rep_item_list.Rows.Count == 0)
        {
            ScriptManager.RegisterStartupScript(Page, GetType(), "popUp", "alert('产品明细不能为空！');", true);//判断产品明细是否为空
            flag = true;
            return flag;
        }
        else
        {
            for (int i = 0; i < rep_item_list.Rows.Count; i++)
            {
                if ((((DropDownList)rep_item_list.Rows[i].FindControl("drpImdeGoodsID")).SelectedItem.Value) == "-1")//判断产品名称是否为空
                {
                    ScriptManager.RegisterStartupScript(Page, GetType(), "popUp", "alert('请输入第" + (i + 1) + "行产品名称！');", true);
                    ((DropDownList)rep_item_list.Rows[i].FindControl("drpImdeGoodsID")).Focus();
                    flag = true;
                    return flag;
                }
                if (((TextBox)rep_item_list.Rows[i].FindControl("txtImdeQuantity")).Text.Trim().Equals(String.Empty))//判断数量是否为空
                {
                    ScriptManager.RegisterStartupScript(Page, GetType(), "popUp", "alert('请输入第" + (i + 1) + "行数量！');", true);
                    ((TextBox)rep_item_list.Rows[i].FindControl("txtImdeQuantity")).Focus();
                    flag = true;
                    return flag;
                }
                Regex r = new Regex("^[0-9]{1,}$");        //判断是否数字
                if (!r.IsMatch(((TextBox)rep_item_list.Rows[i].FindControl("txtImdeQuantity")).Text))      //txtImdeQuantity.Text 这个是要判断的值
                {
                    ScriptManager.RegisterStartupScript(Page, GetType(), "popUp", "alert('数量必须为数字！');", true);
                    ((TextBox)rep_item_list.Rows[i].FindControl("txtImdeQuantity")).Focus();
                    ((TextBox)rep_item_list.Rows[i].FindControl("txtImdeQuantity")).Text = "";
                    flag = true;
                    return flag;
                }
            }
            return flag;
        }