asp.net（文章截取前幾行作為列表摘要）無損返回HTML代碼

復制代碼 代碼如下:
<BR>        /* <STRONG>時間很久遠了，有碼友要，我抄了下來，記得使用的時候還是有部分例外情況要處理，大部分是ok的。</STRONG>
        * 函數： 
        * 說明：無損返回HTML代碼
        *      
        * 作者：卡斯Kas(QQ：10590916)
        * 修改：2010-12-13、
        */

        public static string LeftH(string str, int l)
        {
            //為了防止錯誤
            string odstr = str;
            bool isHtml = false;//判斷截取開頭是否是字符串
            int maxLen = str.Length;
            int n = 0, i = 0, b = 0, e = 0;
            string c, c2 = "", Start = "", EndLabel = "", AllLabel = "";
            if (l >= str.Length) return str;//截取字段大於字符長度

            bool isErr = false;
            try
            {
            while (n < l && i < maxLen)
            {
                //1
                i++;
                c = str.Substring(i - 1, 1);

                string end2str = "";
                try
                {
                    end2str = str.Substring(i - 1, 2);
                }
                catch
                {
                    end2str = "";
                }
                if (c == "<" && end2str != "</")
                {
                    isHtml = true;
                    b = i;//記錄一個位置
                    //5     解決非成對標簽

                    string end2tag = "";
                    try
                    {
                        end2tag = str.Substring(i, 2);
                    }
                    catch
                    {
                        end2tag = "";
                    }

                    if (end2tag == "br")
                    {
                        isHtml = false;
                    }
                    if (str.Substring(i, 1).ToLower() == "%")
                    {
                        isHtml = false;
                    }
                    if (str.Substring(i, 1).ToLower() == "?")
                    {
                        isHtml = false;
                    }
                    else if (end2tag == "hr")
                    {
                        isHtml = false;
                    }
                    //5end
                }
                //1end

                //2
                if (c == "<" && end2str == "</")
                {
                    c2 = str.Substring(i - 1, str.Substring(i - 1).IndexOf(">") + 1);
                    AllLabel = AllLabel.Substring(c2.Length);
                }
                //2end

                Start = Start + c;//記錄當前字符及其前面字符

                if (!isHtml)
                {
                    //6     較為准確的計數
                    try
                    {
                        if (str.Substring(i, 2).ToLower() == "br")
                        {
                        }
                        else if (str.Substring(i, 2).ToLower() == "hr")
                        {
                        }
                        else
                        {
                            n++;
                        }
                    }
                    catch
                    {
                        //如果出錯，則返回純文本(@"<[^>]+>|</[^>]+>");
                        //odstr = Regex.Replace(odstr, @"<[^>]+>|</[^>]+>", "", RegexOptions.IgnoreCase);
                        odstr = odstr.Replace("<", "<").Replace(">", ">");
                        if (l > odstr.Length) l = odstr.Length;
                        return odstr.Substring(0, l);
                    }
                    //6end
                }
                else
                {
                    if (c == ">")//如果循環到>時，要處理的成對標簽中間部分
                    {
                        if (isHtml)
                        {
                            EndLabel = str.Substring(b, i - b);//獲取<到>之間的代碼
                            e = EndLabel.IndexOf(" ");//標簽屬性都有空格，以空格為分割，獲取標簽名
                            if (e > 0)
                            {
                                EndLabel = "</" + EndLabel.Substring(0, e) + ">";
                            }
                            else
                            {
                                EndLabel = "</" + EndLabel;
                            }
                            AllLabel = EndLabel + AllLabel;//記錄當前結束標簽，及所有有關結束標簽
                        }
                        isHtml = false;//重置屬性，從新開始
                    }
                }
                //4     當結束時，發現有未閉合的標簽，則重新來一次
                if (n + 1 >= l)
                {
                    if (InStrN(Start, "<") != InStrN(Start, ">"))
                    {
                        n--;
                    }
                }
                //4end
            }//end while

            }
            catch
            {
                isErr = true;
            }

            string newReString = Start + AllLabel + "...";

            //最後再次驗證
            Regex Rg = new Regex("<.[^>/]+>", RegexOptions.Compiled);
            Regex Rg2 = new Regex(@"<\s*/[a-z]\s*>", RegexOptions.Compiled);

            if (inStrLen(newReString, "<") != inStrLen(newReString, ">"))
            {
                isErr = true;
            }
            else if (inStrLen(newReString.Replace(""", "\""), "\"") % 2 == 1)
            {
                isErr = true;
            }
            else if (Rg.Matches(newReString).Count != Rg2.Matches(newReString).Count)
            {
                isErr = true;
            }
            if (isErr)
            {
                odstr = odstr.Replace("<", "<").Replace(">", ">").Replace("\"", """).Replace("'", "'");
                if (l > odstr.Length)
                { newReString = odstr; }
                else
                {
                    try
                    {
                        newReString = odstr.Substring(0, l) + "...";
                    }
                    catch
                    {
                        newReString = odstr;
                    }
                }
            }

            return newReString;//返回
        }