RSS数据输出格式化字符

    protected string FormatXml(string source)
    {
        StringBuilder sb = new StringBuilder();
        XmlTextWriter writer = null;
        try
        {
            XmlDocument doc = new XmlDocument();
            doc.LoadXml(source);

            writer = new XmlTextWriter(new StringWriter(sb));
            writer.Formatting = Formatting.Indented;

            doc.WriteTo(writer);
        }
        finally
        {
            if (writer != null) writer.Close();
        }
        return sb.ToString();
    }