[C#]숫자 천단위 콤마(,) 표시

        private string AddComma(double dblTemp)
        {
            string strTemp = dblTemp.ToString();

            string strDotUnderGrp = string.Empty;
            string strDotUpGrp = string.Empty;

            if (strTemp.IndexOf('.') > -1)
            {
                strDotUnderGrp = strTemp.Substring(strTemp.IndexOf('.'));
                strDotUpGrp = strTemp.Substring(0, strTemp.IndexOf('.'));
            }
            else
                strDotUpGrp = strTemp;

            if (strDotUpGrp == string.Empty) strDotUpGrp = "0";

            char[] chrDotUpGrpR = strDotUpGrp.ToCharArray();
            Array.Reverse(chrDotUpGrpR);
            string strDotUpGrpR = new string(chrDotUpGrpR);

            int arrCnt = (strDotUpGrpR.Length / 3) + (strDotUpGrpR.Length % 3 > 0 ? 1 : 0);

            string[] strArr = new string[arrCnt];

            for (int i = 0; i < arrCnt; i++)
            {
                if (arrCnt - 1 == i)
                {
                    strArr[i] = strDotUpGrpR.Substring(i * 3);
                    break;
                }
                else
                    strArr[i] = strDotUpGrpR.Substring((i * 3), 3);
            }

            string strArrR = string.Join(",", strArr);

            char[] chrDotUpGrp = strArrR.ToCharArray();
            Array.Reverse(chrDotUpGrp);
            strDotUpGrp = new string(chrDotUpGrp);

            if (strDotUnderGrp.Length > 0)
                return strDotUpGrp + strDotUnderGrp;
            else
                return strDotUpGrp;
        }