asp.net向Google提交Sitemap的代码

这两天给自己网站写了提交sitemap的代码，如果是新手，请过来看，如果是高手，可以不用看。

aspx代码

 1  <tr>
 2                         <td class="detailright" style="150px;">
 3                             生成www开头的课程：
 4                         </td>
 5                         <td class="detailcontent">
 6                             <asp:TextBox runat="server" ID="txtWWWCourseStart" />
 7                             -
 8                             <asp:TextBox runat="server" ID="txtWWWCourseEnd" />
 9                             <asp:Button ID="btnWWWCourse" Text="生成课程XML" runat="server" OnClick="btnWWWCourse_Click" OnClientClick="return CheckWWWCourse();" />
                             [生成的www1-5.xml文件，表示是 http://www.lesson9.com/course/100.html的方式访问课程。]
                         </td>
                     </tr>

cs代码：

protected void btnWWWCourse_Click(object sender, EventArgs e)
        {
            XmlWriterSettings settings = new XmlWriterSettings();
            settings.Indent = true;
            settings.NewLineOnAttributes = true;
            try
            {
                int start = Convert.ToInt32(this.txtWWWCourseStart.Text.Trim());
                int end = Convert.ToInt32(this.txtWWWCourseEnd.Text.Trim());
                XmlTextWriter writer1 = new XmlTextWriter(@"X:\www\www" + start.ToString() + "-" + end.ToString() + ".xml", System.Text.Encoding.UTF8);
                XmlWriter writer = XmlWriter.Create(writer1, settings);

                writer.WriteStartDocument();
                writer.WriteStartElement("urlset");
                writer.WriteAttributeString("xmlns", "http://www.google.com/schemas/sitemap/0.84");

                var r = from i in db.Courses where i.Id <= end && i.Id >= start orderby i.Id ascending select i;
                if (r.Count() > 0)
                {
                    foreach (Lesson9.Entity.Course course in r.ToList())
                    {
                        writer.WriteStartElement("url");
                        writer.WriteElementString("loc", "http://www.XXX.com/course/" + course.Id + ".html");
                        string tempMonth = DateTime.Now.Month.ToString();
                        if (tempMonth.Length == 1)
                        {
                            tempMonth = "0" + tempMonth;
                        }
                        string tempDay = DateTime.Now.Day.ToString();
                        if (tempDay.Length == 1)
                        {
                            tempDay = "0" + tempDay;
                        }
                        writer.WriteElementString("lastmod", DateTime.Now.Year + "-" + tempMonth + "-" + tempDay);
                        writer.WriteElementString("changefreq", "monthly");
                        writer.WriteElementString("priority", "0.5");
                        writer.WriteEndElement();
                    }
                }
                writer.WriteEndElement();
                writer.WriteEndDocument();
                writer.Flush();
                writer.Close();
                this.SetMessageInfo(spanMessage, "成功添加XML文件");
            }
            catch (Exception ex)
            {
                this.SetMessageInfo(spanMessage, "添加出错了："+ ex.Message);
            }
           
        }

另1：XmlWriter writer = XmlWriter.Create(writer1, settings); 如果 writer1是直接文件路径如 d:\TestFolder\TestFile.xml 则settings有效果，不然无效。
哪位知其原，请告诉我。不甚感谢。

另2：google sitemap 暂不支持二级域名的提交，哪位有好方法，欢迎献上来。