除了a10之外,我还需要在我的feed的rss(root)元素中添加新的命名空间：

<rss xmlns:a10="http://www.w3.org/2005/Atom" version="2.0">
    <channel>
.
.
.

我正在使用序列化为RSS 2.0的SyndicationFeed类,我使用XmlWriter输出feed,

var feed = new SyndicationFeed(
                    feedDefinition.Title,
                    feedDefinition.Description,
     .
     .
     .



using (var writer = XmlWriter.Create(context.HttpContext.Response.Output, settings))
        {
            rssFormatter.WriteTo(writer);
        }

我尝试在SyndicationFeed上添加AttributeExtensions,但它添加了新的命名空间
到通道元素而不是根,

谢谢

解决方法:

不幸的是,格式化程序不能以您需要的方式扩展.

您可以使用中间XmlDocument并在写入最终输出之前对其进行修改.

此代码将为最终xml输出的根元素添加命名空间：

var feed = new SyndicationFeed("foo", "bar", new Uri("http://www.example.com"));
var rssFeedFormatter = new Rss20FeedFormatter(feed);

// Create a new  XmlDocument in order to modify the root element
var xmlDoc = new XmlDocument();

// Write the RSS formatted feed directly into the xml doc
using(var xw = xmlDoc.CreateNavigator().AppendChild() )
{
    rssFeedFormatter.WriteTo(xw);
}

// modify the document as you want
xmlDoc.DocumentElement.SetAttribute("xmlns:example", "www.example.com");

// now create your writer and output to it:
var sb = new StringBuilder();
using (XmlWriter writer = XmlWriter.Create(sb))
{
    xmlDoc.WriteTo(writer);
}

Console.WriteLine(sb.ToString());