C#过滤非法字符

    #region 过滤非法字符
    public static string encoding(string src)
    {
        if (src == null)
            return "";
        StringBuilder result = new StringBuilder();
        if (src != null)
        {
            src = src.Trim();
            for (int pos = 0; pos < src.Length; pos++)
            {
                switch (src[pos])
                {
                    case '\"': result.Append("''"); break;

                    case '<': result.Append("<"); break;

                    case '>': result.Append(">"); break;

                    case '\'': result.Append("&apos;"); break;

                    case '&': result.Append("&"); break;

                    case '%': result.Append("&pc;"); break;

                    case '_': result.Append("&ul;"); break;

                    case '#': result.Append("&shap;"); break;

                    case '?': result.Append("&ques;"); break;

                    default: result.Append(src[pos]); break;
                }
            }
        }
        return result.ToString();
    }
    #endregion