How to add image to asp.net rss feed

I am new to rss feeds in asp.net, but I caught on pretty fast on modifying xml in c#. I want to add a image to the rss2.0. Thanks for any help.

Response.Clear();

        Response.ContentType = "text/xml";

        XmlTextWriter xtwFeed = new XmlTextWriter(Response.OutputStream, Encoding.UTF8);

        xtwFeed.WriteStartDocument();

        // The mandatory rss tag

        xtwFeed.WriteStartElement("rss");

        xtwFeed.WriteAttributeString("version", "2.0");

        // The channel tag contains RSS feed details

        xtwFeed.WriteStartElement("channel");

        xtwFeed.WriteElementString("title", "The Latest goole RSS Feeds. Subscribe Today.");

        xtwFeed.WriteElementString("link", "http://googel.com");

        xtwFeed.WriteElementString("image", "http://google.com");

        xtwFeed.WriteElementString("description", "Click on the title to leave a comment.");

        xtwFeed.WriteElem开发者_JAVA百科entString("copyright", "Copyright 2011 google.com. All rights reserved.");
        List<Blog> blogs = (List<Blog>) Blog.GetBlogs();
        foreach (var blog in blogs)
        {
            xtwFeed.WriteStartElement("item");

            xtwFeed.WriteElementString("title", blog.Title);

            xtwFeed.WriteElementString("link",blog.BlogURL);

            if(blog.PictureURL != null || blog.PictureURL != "")
            {

//WANT TO ADD IMAGE HERE xtwFeed.WriteElementString("image", blog.PictureURL);

            }
            xtwFeed.WriteElementString("description", blog.OutputMessage);

            xtwFeed.WriteElementString("copyright", "Copyright 2011 google.com. All rights reserved.");
            xtwFeed.WriteEndElement();
        }
        xtwFeed.WriteEndElement();

        xtwFeed.WriteEndElement();

        xtwFeed.WriteEndDocument();

        xtwFeed.Flush();

        xtwFeed.Close();

        Response.End();

Edit Note: I now have the right format but the image are not showing up

 if(!string.IsNullOrEmpty(blog.PictureURL))
            {
                xtwFeed.WriteStartElement("image");
                xtwFeed.WriteElementString("url", blog.PictureURL);
                xtwFeed.WriteElementString("title", blog.Title);
                xtwFeed.WriteElementString("link", blog.BlogURL);
                xtwFeed.WriteEndElement();
            }

Try this:

xtwFeed.WriteStartElement("enclosure");
 xtwFeed.WriteElementString("url", blog.PictureURL);
 xtwFeed.WriteElementString("type", image/jpeg);
 xtwFeed.WriteEndElement();

i.e. you have to add this element to rss xml

<enclosure url="[PictureURL]" type="image/jpeg"></enclosure>