C#实现文章添加内链的方法

private string keyAddUrl(string src, IList<KeyWord> keys)
    {
      Regex reg = new Regex(@"(?i)(?:^|(?<!<a\b(?>[^<>]*))>)(?>[^<>]*)(?:<|$)");
      int length = 0;
      string temp = string.Empty;
      return reg.Replace(src, delegate (Match m)
      {
        temp = m.Value;
        length = temp.Length;
        for (int i = 0; i < keys.Count; i++)
        {
          string keyWordName = Regex.Escape(keys[i].KeyName);
          string keyWordUrl = Regex.Escape(keys[i].PCUrl);
          temp = Regex.Replace(temp, @"(?is)^((?:(?:(?!" + keyWordName + @"|</?a\b).)*<a\b(?:(?!</?a\b).)*</a>)*(?:(?!" + keyWordName +
            @"|</?a\b).)*)(?<tag>" + keyWordName + @")",
            @"$1<a href=""" rel="external nofollow" + keyWordUrl + @""" target=""_blank"" title=""${tag}"">${tag}</a>");
          if (length != temp.Length)
          {
            keys.Remove(keys[i]);
          }
          length = temp.Length;
        }
        return temp;
      });
    }

/// <summary>
    /// 一键匹配内链，只替换第一个匹配到的字符
    /// </summary>
    /// <param name="content">要匹配的文本字符</param>
    /// <param name="type">判断类型是否是"编辑"</param>
    /// <returns></returns>
    [HttpPost]
    [ValidateInput(false)]
    public async Task<ActionResult> ContentReplace(string content, string type)
    {
      try
      {
        if (type == "edit")
        {
          content = WebHelper.ReplaceStrHref(content);
        }
        if (string.IsNullOrEmpty(content))
        {
          return Content("请输入文本信息");
        }
        var list = await bll.GetAllList();
        if (list != null)
        {
          #region 第二种办法
          // 第一次
          Regex reg = null;
          int n = -1;
          Dictionary<string, string> dic = new Dictionary<string, string>();
          for (int i = 0; i < list.Count; i++)
          {
            if (Regex.Match(content, list[i].KeyName).Success)
            {
              string pattern = $"<a href=\"{list[i].PCUrl}\" target=\"_blank\">{list[i].KeyName}</a>";
              reg = new Regex(list[i].KeyName);
              content = reg.Replace(content, pattern, 1);
              if (Regex.Match(content, pattern).Success)
              {
                //如果当前关键字链接信息成功，将当前的文本链接信息提取出来添加到字典中（dic）,并以唯一标识符代替文本链接信息作为占位符。
                reg = new Regex(pattern);
                n++;
                content = reg.Replace(content, "{" + n + "}", 1);
                dic.Add("{" + n + "}", pattern);
              }
            }
          }
          //将匹配到的文本链接信息format
          if (dic.Count != 0)
          {
            int m = -1;
            foreach (string key in dic.Keys)
            {
              m++;
              if (content.Contains("{" + m + "}"))
              {
                content = content.Replace("{" + m + "}", dic[key]);
              }
            }
          }
          #endregion
          content = WebHelper.RemoveStrImgAlt(content);
          return Content(content);
        }
        else
        {
          throw new Exception("关键字库中没有数据,检查集合是否抛异常了");
        }
      }
      catch (Exception ex)
      {
        throw ex;
      }
    }

/// <summary>
    /// 移除文本字符的a标签
    /// </summary>  
    public static string ReplaceStrHref(string content)
    {
      var r = new Regex(@"<a\s+(?:(?!</a>).)*?>|</a>", RegexOptions.IgnoreCase);
      Match m;
      for (m = r.Match(content); m.Success; m = m.NextMatch())
      {
        content = content.Replace(m.Groups[0].ToString(), "");
      }
      return content;
    }
    /// <summary>
    /// 移除字符文本Img里面Alt关键字包裹的内链
    /// </summary>   
    public static string RemoveStrImgAlt(string content)
    {
      Regex rg2 = new Regex("(?<=alt=\"<a[^<]*)</a>\"");
      if (rg2.Match(content).Success)
      {
        content = rg2.Replace(content, "");
      }
      Regex rg = new Regex("(?<=alt=\")<a href=\"[^>]*>");
      if (rg.Match(content).Success)
      {
        content = rg.Replace(content, "");
      }
      return content;
    }