c#处理转义字符的方法

        private static string ChangeString(string inputStr)
        {
            StringBuilder retVal = new StringBuilder();
            if(inputStr != String.Empty)
            {
                inputStr = inputStr.Trim();
                for(int i=0; i<inputStr.Length; i++)
                {
                    switch   (inputStr[i])
                    {
                        case  '"':  retVal.Append( "&quot; ");   break;
                        case  '&':  retVal.Append( "&amp; ");   break;
                        case  '<':  retVal.Append( "&lt; ");   break;
                        case  '>':  retVal.Append( "&gt; ");   break;
                        default:   retVal.Append(inputStr[i]);   break;
                    }
                }
            }
            return retVal.ToString();
        }
        public string XMLToText(string fString)
        {
            if (fString != string.Empty)
            {
                fString = fString.Replace("&amp;","&");
                fString = fString.Replace("&lt;", " < ");
                fString = fString.Replace("&gt;", " > ");
                fString = fString.Replace("&quot;", ((char)34).ToString());
                fString = fString.Replace("&apos;", " '");
            }
            return fString;
        }