Windows Communication Foundation (WCF) consente di creare un servizio che espone un feed di diffusione. In questo argomento viene illustrato come creare un servizio di diffusione che espone un feed di diffusione RSS.
Per creare un servizio di diffusione di base
Definire un contratto di servizio usando un'interfaccia contrassegnata con l'attributo WebGetAttribute. Ogni operazione esposta come feed di diffusione deve restituire un oggetto Rss20FeedFormatter.
[ServiceContract]
public interface IBlog
{
[OperationContract]
[WebGet]
Rss20FeedFormatter GetBlog();
}
<ServiceContract()> _
Public Interface IBlog
<OperationContract()> _
<WebGet> _
Function GetBlog() As Rss20FeedFormatter
End Interface
public class BlogService : IBlog
{
public Rss20FeedFormatter GetBlog()
{
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 how to sample that demonstrates how to expose a feed using RSS 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;
return new Rss20FeedFormatter(feed);
}
}
Public Class BlogService
Implements IBlog
Public Function GetBlog() As Rss20FeedFormatter Implements IBlog.GetBlog
Dim feed As SyndicationFeed = 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 how to sample that demonstrates how to expose a feed using RSS with WCF")
Dim item1 As SyndicationItem = New SyndicationItem( _
"Item One", _
"This is the content for item one", _
New Uri("http://localhost/Content/One"), _
"ItemOneID", _
DateTime.Now)
Dim item2 As SyndicationItem = New SyndicationItem( _
"Item Two", _
"This is the content for item two", _
New Uri("http://localhost/Content/Two"), _
"ItemTwoID", _
DateTime.Now)
Dim item3 As SyndicationItem = 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
Return New Rss20FeedFormatter(feed)
End Function
End Class
Creare un oggetto SyndicationFeed e aggiungere un autore, una categoria e una descrizione.
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 how to sample that demonstrates how to expose a feed using RSS with WCF");
Dim feed As SyndicationFeed = 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 how to sample that demonstrates how to expose a feed using RSS 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);
Dim item1 As SyndicationItem = New SyndicationItem( _
"Item One", _
"This is the content for item one", _
New Uri("http://localhost/Content/One"), _
"ItemOneID", _
DateTime.Now)
Dim item2 As SyndicationItem = New SyndicationItem( _
"Item Two", _
"This is the content for item two", _
New Uri("http://localhost/Content/Two"), _
"ItemTwoID", _
DateTime.Now)
Dim item3 As SyndicationItem = New SyndicationItem( _
"Item Three", _
"This is the content for item three", _
New Uri("http://localhost/Content/three"), _
"ItemThreeID", _
DateTime.Now)
svcHost.Open()
Console.WriteLine("Service is running")
Dim reader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog")
Dim feed As SyndicationFeed = SyndicationFeed.Load(reader)
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("Summary: {0}", item.Summary.Text)
Next
Console.WriteLine("Press <enter> to quit...")
Console.ReadLine()
svcHost.Close()
Per chiamare GetBlog() con un HTTP GET
In un browser web, navigare sull'URL seguente: http://localhost:8000/BlogService/GetBlog. L'URL contiene l'indirizzo di base del servizio (http://localhost:8000/BlogService), l'indirizzo relativo dell'endpoint e l'operazione del servizio da chiamare.
Per chiamare GetBlog() dal codice
Creare un XmlReader con l'indirizzo di base e il metodo che si sta chiamando.
Uri serviceAddress = new Uri("http://localhost:8000/BlogService/GetBlog");
Dim serviceAddress As New Uri("http://localhost:8000/BlogService/GetBlog")
Dim reader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog")
Dim feed As SyndicationFeed = SyndicationFeed.Load(reader)
Verrà in tal modo richiamata l'operazione del servizio e verrà popolato un nuovo SyndicationFeed con il formattatore restituito dall'operazione del servizio.
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("Summary: {0}", item.Summary.Text)
Next
Esempio
Di seguito è riportato il codice completo per questo esempio.
using System;
using System.Xml;
using System.ServiceModel;
using System.ServiceModel.Description;
using System.ServiceModel.Syndication;
using System.ServiceModel.Web;
using System.Collections.ObjectModel;
using System.Collections.Generic;
namespace Service
{
[ServiceContract]
public interface IBlog
{
[OperationContract]
[WebGet]
Rss20FeedFormatter GetBlog();
}
public class BlogService : IBlog
{
public Rss20FeedFormatter GetBlog()
{
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 how to sample that demonstrates how to expose a feed using RSS 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;
return new Rss20FeedFormatter(feed);
}
}
public class Host
{
static void Main(string[] args)
{
Uri baseAddress = new Uri("http://localhost:8000/BlogService");
WebServiceHost svcHost = new WebServiceHost(typeof(BlogService), baseAddress);
try
{
svcHost.Open();
Console.WriteLine("Service is running");
XmlReader reader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog");
SyndicationFeed feed = SyndicationFeed.Load(reader);
Console.WriteLine(feed.Title.Text);
Console.WriteLine("Items:");
foreach (SyndicationItem item in feed.Items)
{
Console.WriteLine("Title: {0}", item.Title.Text);
Console.WriteLine("Summary: {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();
}
}
}
}
Imports System.Xml
Imports System.ServiceModel
Imports System.ServiceModel.Description
Imports System.ServiceModel.Syndication
Imports System.ServiceModel.Web
Imports System.Collections.ObjectModel
Imports System.Collections.Generic
<ServiceContract()> _
Public Interface IBlog
<OperationContract()> _
<WebGet> _
Function GetBlog() As Rss20FeedFormatter
End Interface
Public Class BlogService
Implements IBlog
Public Function GetBlog() As Rss20FeedFormatter Implements IBlog.GetBlog
Dim feed As SyndicationFeed = 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 how to sample that demonstrates how to expose a feed using RSS with WCF")
Dim item1 As SyndicationItem = New SyndicationItem( _
"Item One", _
"This is the content for item one", _
New Uri("http://localhost/Content/One"), _
"ItemOneID", _
DateTime.Now)
Dim item2 As SyndicationItem = New SyndicationItem( _
"Item Two", _
"This is the content for item two", _
New Uri("http://localhost/Content/Two"), _
"ItemTwoID", _
DateTime.Now)
Dim item3 As SyndicationItem = 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
Return New Rss20FeedFormatter(feed)
End Function
End Class
Module Program
Sub Main()
Dim baseAddress As New Uri("http://localhost:8000/BlogService")
Dim svcHost As New WebServiceHost(GetType(BlogService), baseAddress)
Try
svcHost.Open()
Console.WriteLine("Service is running")
Dim reader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog")
Dim feed As SyndicationFeed = SyndicationFeed.Load(reader)
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("Summary: {0}", item.Summary.Text)
Next
Console.WriteLine("Press <enter> to quit...")
Console.ReadLine()
svcHost.Close()
Catch ce As CommunicationException
Console.WriteLine("An exception occurred: {0}", ce.Message)
svcHost.Abort()
End Try
End Sub
End Module
Compilazione del codice
Durante la compilazione del codice precedente, fare riferimento a System.ServiceModel.dll e a System.ServiceModel.Web.dll.
Utilizzare un servizio Web REST con HttpClient ed eseguire operazioni CRUD di base. Si rileverà quando il dispositivo è connesso a Internet per offrire un'esperienza utente ottimale e sfruttare gli stack di rete nativi per ottenere prestazioni ottimali.