如何修复“x 是一个变量，但像方法一样使用"C#中的语法错误?

我在处理 gradrid 页脚总计时遇到以下错误'fitem' 是一个'变量'，但用作'方法'"

I am getting the following error working on gradrid footer totals "'fitem' is a 'variable' but is used like a 'method'"

protected void RadGrid1_ItemDataBound(object sender, Telerik.Web.UI.GridItemEventArgs e)
{
    if (e.Item is GridFooterItem)
    {
        GridFooterItem fitem = (e.Item as GridFooterItem);
        string value1 = fitem("CALENDAR_DAYS_MTD").Text;
        string value2 = fitem("WEEKENDS_MTD").Text;
        string value3 = fitem("HOLIDAYS_MTD").Text;
        string value4 = fitem("BUSINESS_DAYS_MTD").Text;
        int footervalue1 = Convert.ToInt32(value1.Split(':')[1]);
        int footervalue2 = Convert.ToInt32(value2.Split(':')[1]);
        int footervalue3 = Convert.ToInt32(value3.Split(':')[1]);
        int footervalue4 = Convert.ToInt32(value4.Split(':')[1]);
        //to get the value only.
        if (footervalue2 + footervalue3 + footervalue4 > footervalue1)
        {
            fitem("WEEKENDS_MTD").Style("color") = "Black";
            fitem("HOLIDAYS_MTD").Style("color") = "Black";
            fitem("BUSINESS_DAYS_MTD").Style("color") = "Black";


        }
        else
        {
            fitem("WEEKENDS_MTD").Style("color") = "Red";
            fitem("HOLIDAYS_MTD").Style("color") = "Red";
            fitem("BUSINESS_DAYS_MTD").Style("color") = "Red";
        }
    }
}