如何从Web API方法返回Xml数据？

Question

我有一个Web Api方法，它应返回一个xml数据，但它返回字符串：

 public class HealthCheckController : ApiController
    {       
        [HttpGet]
        public string Index()
        {
            var healthCheckReport = new HealthCheckReport();

            return healthCheckReport.ToXml();
        }
    }

它返回：

<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">
<myroot><mynode></mynode></myroot>
</string>

我添加了这个映射：

 config.Routes.MapHttpRoute(
              name: "HealthCheck",
              routeTemplate: "healthcheck",
              defaults: new
              {
                  controller = "HealthCheck",
                  action = "Index"
              });

如何使它只返回xml位：

<myroot><mynode></mynode></myroot>

如果我只使用MVC，我可以使用下面的内容，但Web API不支持“内容”：

 [HttpGet]
        public ActionResult Index()
        {
            var healthCheckReport = new HealthCheckReport();

            return Content(healthCheckReport.ToXml(), "text/xml");
        }

我还在WebApiConfig类中添加了以下代码：

 config.Formatters.Remove(config.Formatters.JsonFormatter);
 config.Formatters.XmlFormatter.UseXmlSerializer = true;

Answer 1

这是最快的方式，

 public class HealthCheckController : ApiController
 {       
     [HttpGet]
     public HttpResponseMessage Index()
     {
         var healthCheckReport = new HealthCheckReport();

         return new HttpResponseMessage() {Content = new StringContent( healthCheckReport.ToXml(), Encoding.UTF8, "application/xml" )};
     }
 }

但是构建一个新的XmlContent类也非常容易，该类派生自HttpContent以直接支持XmlDocument或XDocument。 例如

public class XmlContent : HttpContent
{
    private readonly MemoryStream _Stream = new MemoryStream();

    public XmlContent(XmlDocument document) {
        document.Save(_Stream);
            _Stream.Position = 0;
        Headers.ContentType = new MediaTypeHeaderValue("application/xml");
    }

    protected override Task SerializeToStreamAsync(Stream stream, System.Net.TransportContext context) {

        _Stream.CopyTo(stream);

        var tcs = new TaskCompletionSource<object>();
        tcs.SetResult(null);
        return tcs.Task;
    }

    protected override bool TryComputeLength(out long length) {
        length = _Stream.Length;
        return true;
    }
}

并且您可以像使用StreamContent或StringContent一样使用它，除了它接受XmlDocument，

public class HealthCheckController : ApiController
{       
    [HttpGet]
    public HttpResponseMessage Index()
    {
       var healthCheckReport = new HealthCheckReport();

       return new HttpResponseMessage() {
           RequestMessage = Request,
           Content = new XmlContent(healthCheckReport.ToXmlDocument()) };
    }
}