如何：作为 Atom 和 RSS 公开源

使用 Windows Communication Foundation (WCF) 可以创建公开联合源的服务。 本主题讨论如何使用 Atom 1.0 和 RSS 2.0 创建公开联合源的联合服务。 此服务公开一个可以返回任一联合格式的终结点。 为了简单起见，本示例中使用的服务为自承载服务。 在生产环境中，此类型的服务将承载在 IIS 或 WAS 下。 有关不同 WCF 托管选项的详细信息，请参阅托管。

创建基本联合服务

1. 使用通过 WebGetAttribute 属性标记的接口定义服务协定。 作为联合源公开的每个操作都会返回一个 SyndicationFeedFormatter 对象。 请注意 WebGetAttribute 的参数。 UriTemplate 指定用于调用此服务操作的 URL。 此参数的字符串包含文本和一个用大括号括起的变量 ({format})。 此变量与服务操作的 format 参数相对应。 有关详细信息，请参阅 UriTemplate。 BodyStyle 会影响此服务操作所发送和接收的消息的写入方式。 Bare 指定不使用基础结构定义的 XML 元素包装发送到和接收自此服务操作的数据。 有关详细信息，请参阅 WebMessageBodyStyle。

   [ServiceContract]
   [ServiceKnownType(typeof(Atom10FeedFormatter))]
   [ServiceKnownType(typeof(Rss20FeedFormatter))]
   public interface IBlog
   {
       [OperationContract]
       [WebGet(UriTemplate = "GetBlog?format={format}")]
       SyndicationFeedFormatter GetBlog(string format);
   }
   

   <ServiceContract()> _
   <ServiceKnownType(GetType(Atom10FeedFormatter))> _
   <ServiceKnownType(GetType(Rss20FeedFormatter))> _
   Public Interface IBlog
       <OperationContract()> _
       <WebGet(UriTemplate:="GetBlog?format={format}")> _
       Function GetBlog(ByVal format As String) As SyndicationFeedFormatter
   End Interface
   

   注意

   在此接口中使用 ServiceKnownTypeAttribute 以指定服务操作返回的类型。

2. 实现服务协定。

   public class BlogService : IBlog
   {
       public SyndicationFeedFormatter GetBlog(string format)
       {
           SyndicationFeed feed = new SyndicationFeed("My Blog Feed", "This is a test feed", new Uri("http://SomeURI"));
           feed.Authors.Add(new SyndicationPerson("someone@microsoft.com"));
           feed.Categories.Add(new SyndicationCategory("How To Sample Code"));
           feed.Description = new TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF");
           SyndicationItem item1 = new SyndicationItem(
               "Item One",
               "This is the content for item one",
               new Uri("http://localhost/Content/One"),
               "ItemOneID",
               DateTime.Now);
   
           SyndicationItem item2 = new SyndicationItem(
               "Item Two",
               "This is the content for item two",
               new Uri("http://localhost/Content/Two"),
               "ItemTwoID",
               DateTime.Now);
   
           SyndicationItem item3 = new SyndicationItem(
               "Item Three",
               "This is the content for item three",
               new Uri("http://localhost/Content/three"),
               "ItemThreeID",
               DateTime.Now);
           List<SyndicationItem> items = new List<SyndicationItem>();
           items.Add(item1);
           items.Add(item2);
           items.Add(item3);
   
           feed.Items = items;
   
           if (format == "rss")
               return new Rss20FeedFormatter(feed);
           else if (format == "atom")
               return new Atom10FeedFormatter(feed);
           else return null;
       }
   }
   

   Public Class BlogService
       implements IBlog
   
       Public Function GetBlog(ByVal format As String) As SyndicationFeedFormatter Implements IBlog.GetBlog
           Dim feed As New SyndicationFeed("My Blog Feed", "This is a test feed", New Uri("http://SomeURI"))
           feed.Authors.Add(New SyndicationPerson("someone@microsoft.com"))
           feed.Categories.Add(New SyndicationCategory("How To Sample Code"))
           feed.Description = New TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF")
           Dim item1 As New SyndicationItem( _
               "Item One", _
               "This is the content for item one", _
               New Uri("http://localhost/Content/One"), _
               "ItemOneID", _
               DateTime.Now)
   
           Dim item2 As New SyndicationItem( _
               "Item Two", _
               "This is the content for item two", _
               New Uri("http://localhost/Content/Two"), _
               "ItemTwoID", _
               DateTime.Now)
   
           Dim item3 As New SyndicationItem( _
               "Item Three", _
               "This is the content for item three", _
               New Uri("http://localhost/Content/three"), _
               "ItemThreeID", _
               DateTime.Now)
           Dim items As New List(Of SyndicationItem)()
           items.Add(item1)
           items.Add(item2)
           items.Add(item3)
   
           feed.Items = items
   
           If (format = "rss") Then
               Return New Rss20FeedFormatter(feed)
           Else
               Return New Atom10FeedFormatter(feed)
           End If
       End Function
   End Class
   

3. 创建 SyndicationFeed 对象，并添加作者、类别和说明。

   SyndicationFeed feed = new SyndicationFeed("My Blog Feed", "This is a test feed", new Uri("http://SomeURI"));
   feed.Authors.Add(new SyndicationPerson("someone@microsoft.com"));
   feed.Categories.Add(new SyndicationCategory("How To Sample Code"));
   feed.Description = new TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF");
   

   Dim feed As New SyndicationFeed("My Blog Feed", "This is a test feed", New Uri("http://SomeURI"))
   feed.Authors.Add(New SyndicationPerson("someone@microsoft.com"))
   feed.Categories.Add(New SyndicationCategory("How To Sample Code"))
   feed.Description = New TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF")
   

4. 创建若干 SyndicationItem 对象。

   SyndicationItem item1 = new SyndicationItem(
       "Item One",
       "This is the content for item one",
       new Uri("http://localhost/Content/One"),
       "ItemOneID",
       DateTime.Now);
   
   SyndicationItem item2 = new SyndicationItem(
       "Item Two",
       "This is the content for item two",
       new Uri("http://localhost/Content/Two"),
       "ItemTwoID",
       DateTime.Now);
   
   SyndicationItem item3 = new SyndicationItem(
       "Item Three",
       "This is the content for item three",
       new Uri("http://localhost/Content/three"),
       "ItemThreeID",
       DateTime.Now);
   

   Dim item1 As New SyndicationItem( _
       "Item One", _
       "This is the content for item one", _
       New Uri("http://localhost/Content/One"), _
       "ItemOneID", _
       DateTime.Now)
   
   Dim item2 As New SyndicationItem( _
       "Item Two", _
       "This is the content for item two", _
       New Uri("http://localhost/Content/Two"), _
       "ItemTwoID", _
       DateTime.Now)
   
   Dim item3 As New SyndicationItem( _
       "Item Three", _
       "This is the content for item three", _
       New Uri("http://localhost/Content/three"), _
       "ItemThreeID", _
       DateTime.Now)
   

5. 向源中添加 SyndicationItem 对象。

   List<SyndicationItem> items = new List<SyndicationItem>();
   items.Add(item1);
   items.Add(item2);
   items.Add(item3);
   
   feed.Items = items;
   

   Dim items As New List(Of SyndicationItem)()
   items.Add(item1)
   items.Add(item2)
   items.Add(item3)
   
   feed.Items = items
   

6. 使用格式参数返回请求的格式。

   if (format == "rss")
       return new Rss20FeedFormatter(feed);
   else if (format == "atom")
       return new Atom10FeedFormatter(feed);
   else return null;
   

   If (format = "rss") Then
       Return New Rss20FeedFormatter(feed)
   Else
       Return New Atom10FeedFormatter(feed)
   End If
   

承载服务

1. 创建 WebServiceHost 对象。 除非在代码或配置中指定了一个终结点，WebServiceHost 类会自动在服务的基地址添加终结点。 在此示例中，不指定任何终结点，因此公开默认终结点。

   Uri address = new Uri("http://localhost:8000/BlogService/");
   WebServiceHost svcHost = new WebServiceHost(typeof(BlogService), address);
   

   Dim address As New Uri("http://localhost:8000/BlogService/")
   Dim svcHost As New WebServiceHost(GetType(BlogService), address)
   

2. 打开服务主机，从服务加载源，显示源，然后等待用户按 Enter。

   svcHost.Open();
   Console.WriteLine("Service is running");
   
   Console.WriteLine("Loading feed in Atom 1.0 format.");
   XmlReader atomReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom");
   SyndicationFeed atomFeed = SyndicationFeed.Load(atomReader);
   Console.WriteLine(atomFeed.Title.Text);
   Console.WriteLine("Items:");
   foreach (SyndicationItem item in atomFeed.Items)
   {
       Console.WriteLine("Title: {0}", item.Title.Text);
       Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Content).Text);
   }
   
   Console.WriteLine("Loading feed in RSS 2.0 format.");
   XmlReader rssReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=rss");
   SyndicationFeed rssFeed = SyndicationFeed.Load(rssReader);
   Console.WriteLine(rssFeed.Title.Text);
   Console.WriteLine("Items:");
   foreach (SyndicationItem item in rssFeed.Items)
   {
       Console.WriteLine("Title: {0}", item.Title.Text);
       // Notice we are using item.Summary here instead of item.Content. This is because
       // of the differences between Atom 1.0 and RSS 2.0 specs.
       Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Summary).Text);
   }
   
   Console.WriteLine("Press <ENTER> to quit...");
   Console.ReadLine();
   svcHost.Close();
   

   svcHost.Open()
   Console.WriteLine("Service is running")
   
   Console.WriteLine("Loading feed in Atom 1.0 format.")
   Dim atomReader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom")
   Dim atomFeed As SyndicationFeed = SyndicationFeed.Load(atomReader)
   Console.WriteLine(atomFeed.Title.Text)
   Console.WriteLine("Items:")
   For Each item As SyndicationItem In atomFeed.Items
       Console.WriteLine("Title: {0}", item.Title.Text)
       Console.WriteLine("Content: {0}", CType(item.Content, TextSyndicationContent).Text)
   Next
   
   Console.WriteLine("Loading feed in RSS 2.0 format.")
   Dim rssReader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=rss")
   Dim rssFeed As SyndicationFeed = SyndicationFeed.Load(rssReader)
   Console.WriteLine(rssFeed.Title.Text)
   Console.WriteLine("Items:")
   For Each item As SyndicationItem In rssFeed.Items
       Console.WriteLine("Title: {0}", item.Title.Text)
       Console.WriteLine("Content: {0}", CType(item.Content, TextSyndicationContent).Text)
   Next
   
   
   Console.WriteLine("Press <ENTER> to quit...")
   Console.ReadLine()
   svcHost.Close()
   

使用 HTTP GET 调用 GetBlog

1. 打开一个浏览器，输入以下 URL，然后按 Enter：http://localhost:8000/BlogService/GetBlog。

   URL 包含服务的基址 (http://localhost:8000/BlogService)、终结点的相对地址，以及要调用的服务操作。

从代码中调用 GetBlog()

1. 使用基址和调用的方法创建 XmlReader。

   XmlReader reader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom");
   

   Dim atomReader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom")
   

2. 调用静态 Load(XmlReader) 方法，同时传入刚刚创建的 XmlReader。

   SyndicationFeed feed = SyndicationFeed.Load(reader);
   

   Dim feed As SyndicationFeed = SyndicationFeed.Load(atomReader)
   

   这将调用服务操作，并用从服务操作返回的格式化程序填充新的 SyndicationFeed。

3. 访问源对象。

   Console.WriteLine(feed.Title.Text);
   Console.WriteLine("Items:");
   foreach (SyndicationItem item in feed.Items)
   {
       Console.WriteLine("Title: {0}", item.Title.Text);
       Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Content).Text);
   }
   

   Console.WriteLine(feed.Title.Text)
   Console.WriteLine("Items:")
   For Each item As SyndicationItem In feed.Items
       Console.WriteLine("Title: {0}", item.Title.Text)
       Console.WriteLine("Content: {0}", (CType(item.Content, TextSyndicationContent).Text))
   Next
   

示例

下面列出了此示例的完整代码。

using System;
using System.Xml;
using System.Collections.Generic;
using System.ServiceModel;
using System.ServiceModel.Description;
using System.ServiceModel.Syndication;
using System.ServiceModel.Web;
namespace Service
{
    [ServiceContract]
    [ServiceKnownType(typeof(Atom10FeedFormatter))]
    [ServiceKnownType(typeof(Rss20FeedFormatter))]
    public interface IBlog
    {
        [OperationContract]
        [WebGet(UriTemplate = "GetBlog?format={format}")]
        SyndicationFeedFormatter GetBlog(string format);
    }

    public class BlogService : IBlog
    {
        public SyndicationFeedFormatter GetBlog(string format)
        {
            SyndicationFeed feed = new SyndicationFeed("My Blog Feed", "This is a test feed", new Uri("http://SomeURI"));
            feed.Authors.Add(new SyndicationPerson("someone@microsoft.com"));
            feed.Categories.Add(new SyndicationCategory("How To Sample Code"));
            feed.Description = new TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF");
            SyndicationItem item1 = new SyndicationItem(
                "Item One",
                "This is the content for item one",
                new Uri("http://localhost/Content/One"),
                "ItemOneID",
                DateTime.Now);

            SyndicationItem item2 = new SyndicationItem(
                "Item Two",
                "This is the content for item two",
                new Uri("http://localhost/Content/Two"),
                "ItemTwoID",
                DateTime.Now);

            SyndicationItem item3 = new SyndicationItem(
                "Item Three",
                "This is the content for item three",
                new Uri("http://localhost/Content/three"),
                "ItemThreeID",
                DateTime.Now);
            List<SyndicationItem> items = new List<SyndicationItem>();
            items.Add(item1);
            items.Add(item2);
            items.Add(item3);

            feed.Items = items;

            if (format == "rss")
                return new Rss20FeedFormatter(feed);
            else if (format == "atom")
                return new Atom10FeedFormatter(feed);
            else return null;
        }
    }

    public class Host
    {
        static void Main(string[] args)
        {
            Uri address = new Uri("http://localhost:8000/BlogService/");
            WebServiceHost svcHost = new WebServiceHost(typeof(BlogService), address);
            try
            {
                svcHost.Open();
                Console.WriteLine("Service is running");

                Console.WriteLine("Loading feed in Atom 1.0 format.");
                XmlReader atomReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom");
                SyndicationFeed atomFeed = SyndicationFeed.Load(atomReader);
                Console.WriteLine(atomFeed.Title.Text);
                Console.WriteLine("Items:");
                foreach (SyndicationItem item in atomFeed.Items)
                {
                    Console.WriteLine("Title: {0}", item.Title.Text);
                    Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Content).Text);
                }

                Console.WriteLine("Loading feed in RSS 2.0 format.");
                XmlReader rssReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=rss");
                SyndicationFeed rssFeed = SyndicationFeed.Load(rssReader);
                Console.WriteLine(rssFeed.Title.Text);
                Console.WriteLine("Items:");
                foreach (SyndicationItem item in rssFeed.Items)
                {
                    Console.WriteLine("Title: {0}", item.Title.Text);
                    // Notice we are using item.Summary here instead of item.Content. This is because
                    // of the differences between Atom 1.0 and RSS 2.0 specs.
                    Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Summary).Text);
                }

                Console.WriteLine("Press <ENTER> to quit...");
                Console.ReadLine();
                svcHost.Close();
            }
            catch (CommunicationException ce)
            {
                Console.WriteLine("An exception occurred: {0}", ce.Message);
                svcHost.Abort();
            }
        }
    }
}

编译代码

编译前面的代码时，请引用 System.ServiceModel.dll 和 System.ServiceModel.Web.dll。

另请参阅

• WebHttpBinding
• WebGetAttribute