.NET ServiceModel.Syndication - RSS源上的更改编码

Question

我正试图解决一个错误，在http://captainobvio.us中，我正在生成的所有RSS提要都会在Internet (版本8和9)中产生以下错误：

不支持从当前编码切换到指定编码的

源代码错误切换。行:1字符: 40

问题是，通过HTTP报头发送的实际编码类型与文档声明的不同。下面是我的代码，用于将提要的输出写入HTML：

public ContentResult Index()
        {
            var feed = _syndication.SyndicateIdeas(_repository.GetIdeas(0,15).Ideas);

            var sb = new StringBuilder();
            using (var writer = XmlWriter.Create(sb, new XmlWriterSettings { Encoding = Encoding.UTF8, NewLineHandling = NewLineHandling.Entitize, NewLineOnAttributes = true, Indent = true}))
            {
                feed.SaveAsRss20(writer);
                writer.Close();
            }

            return Content(sb.ToString(), "application/rss+xml", Encoding.UTF8);
        } 

下面是使用System.ServiceModel.Syndication在.NET 4.0中实际构建提要的代码：

var feed = new SyndicationFeed("CaptainObvio.us - Recent Ideas",
                                          "The most recent ideas posted by the Community on CaptainObvio.us", new Uri("http://captainobvio.us/"), "CaptainObvio.us", new DateTimeOffset(ideas[0].DatePosted), items)
                           {
                               Generator = "CaptainObvio.us - http://captainobvio.us/"
                           };

            return feed;

我想要做的是将XML文档改为utf-8，而不是utf-16。我还检查了编码命名空间，以确定是否有UTF16选项(这样我就可以更正header而不是XML )，但是找不到。

是否有一种简单的方法直接从System.ServiceModel.Syndication更改XML文档上的编码属性？解决这个问题最简单的方法是什么？

Answer 1

之所以会发生这种情况，是因为您要将一个StringBuilder传递给XmlWriter构造函数。.NET中的字符串是unicode，因此XmlWriter假设utf-16，您不能修改它。

因此，您可以使用流而不是字符串生成器，然后可以使用以下设置来控制编码：

var settings = new XmlWriterSettings 
{ 
    Encoding = Encoding.UTF8, 
    NewLineHandling = NewLineHandling.Entitize, 
    NewLineOnAttributes = true, 
    Indent = true 
};
using (var stream = new MemoryStream())
using (var writer = XmlWriter.Create(stream, settings))
{
    feed.SaveAsRss20(writer);
    writer.Flush();
    return File(stream.ToArray(), "application/rss+xml; charset=utf-8");
}

所有这一切--更好的、更多的MVCish --以及我推荐的解决方案是编写一个SyndicationResult

public class SyndicationResult : ActionResult
{
    private readonly SyndicationFeed _feed;
    public SyndicationResult(SyndicationFeed feed)
    {
        if (feed == null)
        {
            throw new HttpException(401, "Not found");
        }
        _feed = feed;
    }

    public override void ExecuteResult(ControllerContext context)
    {
        var settings = new XmlWriterSettings
        {
            Encoding = Encoding.UTF8,
            NewLineHandling = NewLineHandling.Entitize,
            NewLineOnAttributes = true,
            Indent = true
        };

        var response = context.HttpContext.Response;
        response.ContentType = "application/rss+xml; charset=utf-8";
        using (var writer = XmlWriter.Create(response.OutputStream, settings))
        {
            _feed.SaveAsRss20(writer);
        }
    }
}

在控制器操作中，只需返回此结果，这样就不会将控制器操作与管道代码混淆：

public ActionResult Index()
{
    var ideas = _repository.GetIdeas(0, 15).Ideas;
    var feed = _syndication.SyndicateIdeas(ideas);
    return new SyndicationResult(feed);
}