代码如下：

      private string GetHttpStr(string str, string httpStr)

        {

            bool Ishavevalue = false;

            int newlength = httpStr.Length;

            string newstr = null;

            string httpendString = "<";

             if (str.Length >= newlength && str.Contains(httpStr))

            {

                newstr = str.Substring(str.IndexOf(httpStr, StringComparison.OrdinalIgnoreCase) + newlength);

            }

            int startindex = 0;

            startindex = str.IndexOf(httpStr, StringComparison.OrdinalIgnoreCase);

            int lengthindex = 0;

            string returnvalue = null;

            if (startindex >= 0)

            {

                if (newstr.IndexOf('"') != -1 && newstr.IndexOf('"') <= newstr.IndexOf(httpendString))

                {

                    lengthindex = newstr.IndexOf('"') + newlength;

                }

                else if (newstr.IndexOf('"') == -1 && newstr.IndexOf(httpendString) == -1)

                {

                    lengthindex = str.Length;

                }

                else

                {

                    lengthindex = newstr.IndexOf(httpendString) + newlength;

                }

                if (lengthindex == (newlength - 1))

                {

                    lengthindex = newstr.IndexOf(httpendString) + newlength;

                }

                returnvalue = str.Substring(startindex, lengthindex);

                Ishavevalue = true;

            }

            returnvalue = ReplaceSpecialUrl(returnvalue);

            return returnvalue + "  " + ((startindex + lengthindex) < str.Length && startindex > 0 && Ishavevalue ? GetHttpStr(str.Substring(startindex + lengthindex), httpStr) : null);

        }

因为HTTP连接在html都是以"结束或者<结束，所以根据传入的httpStr样式不区分大小写方式把字符串str含有的以递归的方式找出来。