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ASP.net 关健词加链接

/// <summary> 
    /// 为关键词加上超链接 
    /// </summary> 
    /// e.g.:  
    /// string result=GetInnertLink("<a href="http//www.baidu.com" mce_href="http/www.baidu.com">Ningxi</a>Xi过得<span>XI<span>好<a href="http://www.yanhan89.com" mce_href=http://www.jjiale.cn>家政网</a>!","xi","ningxi","http://www.yanhan89.com","_blank",0
    /// <param name="htmlcode">要把关键词加上超链接的html源文本</param> 
    /// <param name="keyword">将要加上超链接的关键词</param> 
    /// <param name="title">将要加上的超链接的描文本</param> 
    /// <param name="url">将要加上的超链接的url地址</param> 
    /// <param name="target">将要加上的超链接的打开方式</param> 
    /// <param name="num">为html文本内的前num个关键词加上超链接,0代表全加上超链接</param> 
    /// <returns>返回为关键词加上超链接后的html文本</returns> 
    public static string GetInnertLink(string htmlcode, string keyword, string title, string url, string target, int num)
    {
        string htmlcodeResult = htmlcode;  //用于保存最新的html文本
        string htmlcodeLower = htmlcodeResult.ToLower();  //用于保存最新的Hmtl文本的小写,方便不分大小写找出关键词
        string keywordResult = "";  //用于保存关键词的原来面貌,可能是大写,或者有大也有小
        int keyIndex = 0;           //关键词所在位置
        int currentIndex = 0;       //每次搜索关键词的开始位置
        int currentNum = 0;         //保存当前加上了多少个有效超链接
        int LBracketIndex = 0;      //左尖括号<位置
        int RBracketIndex = 0;      //右尖括号>位置
        if (num == 0)
        {
            num = htmlcode.Length;
        }
        while (currentIndex <= htmlcodeLower.Length && currentNum < num)
        {
            if (htmlcodeLower.IndexOf(keyword.ToLower(), currentIndex) > -1)
            {
                keyIndex = htmlcodeLower.IndexOf(keyword.ToLower(), currentIndex);
                LBracketIndex = keyIndex;
                do
                {
                    LBracketIndex = htmlcodeLower.LastIndexOf("<", LBracketIndex - 1, LBracketIndex - currentIndex);
                }
                while (LBracketIndex != -1 && htmlcodeLower.Substring(LBracketIndex + 1, 1) == "/");
                RBracketIndex = htmlcodeLower.LastIndexOf(">", keyIndex - 1, keyIndex - currentIndex);
                if (LBracketIndex <= RBracketIndex)
                {
                    //不在标签的属性内,可以有在标签开始与结束标志内,或在开始与结束标志外 
                    LBracketIndex = htmlcodeLower.LastIndexOf("<", keyIndex - 1, keyIndex - currentIndex);
                    if (LBracketIndex != -1 && htmlcodeLower.Substring(LBracketIndex + 1, 1) != "/")
                    {
                        //在开始与结束标志内 
                        //关键词在开始标签与结束标签内,要再判定是不是a标签或pre标签 
                        if (htmlcodeLower.Substring(LBracketIndex + 1, 1) == "a" || htmlcodeLower.Substring(LBracketIndex + 3, 3) == "pre")
                        {
                            //关键词在开始与结束a标签或pre标签内,不可加超链接,循环再来 
                            currentIndex = keyIndex + keyword.Length;
                        }
                        else
                        {
                            //可以加超链接 
                            keywordResult = htmlcodeResult.Substring(keyIndex, keyword.Length);
                            htmlcodeResult = htmlcodeResult.Remove(keyIndex, keyword.Length);
                            htmlcodeResult = htmlcodeResult.Insert(keyIndex, "<a href=''" + url + "''  title=''" + title + "'' target=''" + target + "''>" + keywordResult + "</a>");
                            htmlcodeLower = htmlcodeResult.ToLower();
                            currentIndex = htmlcodeResult.IndexOf("</a>", keyIndex) + 4;
                            currentNum += 1;
                        }
                    }
                    else if ((RBracketIndex = htmlcodeLower.LastIndexOf(">", keyIndex - 1, keyIndex - currentIndex)) != -1)
                    {
                        //
                        // 当查找范围内存在''>''标签则说明在一个静态控件中则需要判断这个控件是否是a标签
                        //
                        if (htmlcodeLower.Substring(htmlcodeLower.IndexOf(''<'', currentIndex) + 1, 2) == "/a")
                        {
                            //关键词在a标签内则不能添加超链接
                            currentIndex = keyIndex + keyword.Length;
                        }
                    }
                    else
                    {
                        //在结束标志外,可以加超链接 
                        keywordResult = htmlcodeResult.Substring(keyIndex, keyword.Length);
                        htmlcodeResult = htmlcodeResult.Remove(keyIndex, keyword.Length);
                        htmlcodeResult = htmlcodeResult.Insert(keyIndex, "<a href=''" + url + "'' title=''" + title + "'' target=''" + target + "''>" + keywordResult + "</a>");
                        htmlcodeLower = htmlcodeResult.ToLower();
                        currentIndex = htmlcodeResult.IndexOf("</a>", keyIndex) + 4;
                        currentNum += 1;
                    }
                }
                else
                {
                    //关键词是标签内的属性值,不可加超链接,循环再来 
                    currentIndex = keyIndex + keyword.Length;
                }
            }
            else
            {
                currentIndex = htmlcodeLower.Length + 1;
            }
        }
        return htmlcodeResult;
    }

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