方法: 基本的な RSS フィードを作成する

[アーティクル]
04/03/2023

Windows Communication Foundation (WCF) では、配信フィードを公開するサービスを作成できます。ここでは、RSS 配信フィードを公開する配信サービスを作成する方法について説明します。

基本的な配信サービスを作成するには

WebGetAttribute 属性でマークされたインターフェイスを使用して、サービスコントラクトを定義します。配信フィードとして公開される各操作は、Rss20FeedFormatter オブジェクトを返す必要があります。
```
[ServiceContract]
public interface IBlog
{
    [OperationContract]
    [WebGet]
    Rss20FeedFormatter GetBlog();
}
```
```
<ServiceContract()> _
Public Interface IBlog
    <OperationContract()> _
    <WebGet> _
    Function GetBlog() As Rss20FeedFormatter
End Interface
```
Note

WebGetAttribute 属性を適用するすべてのサービス操作は、HTTP GET 要求にマッピングされます。他の HTTP メソッドに操作をマッピングするには、代わりに WebInvokeAttribute を使用します。詳細については、「方法: 基本的な WCF Web HTTP サービスを作成する」を参照してください。

サービスコントラクトを実装します。

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

SyndicationFeed オブジェクトを作成し、作成者、カテゴリ、および説明を追加します。

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")

複数の SyndicationItem オブジェクトを作成します。

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)

SyndicationItem をフィードに追加します。

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

フィードを返します。

return new Rss20FeedFormatter(feed);

Return New Rss20FeedFormatter(feed)

サービスをホストするには

WebServiceHost オブジェクトを作成します。

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

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

サービスホストを開き、ユーザーが Enter キーを押すのを待ちます。

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();

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()

HTTP GET で GetBlog() を呼び出すには

Web ブラウザーで、次の URL を参照します: http://localhost:8000/BlogService/GetBlog。この URL には、サービスのベースアドレス (http://localhost:8000/BlogService)、エンドポイントの相対アドレス、および呼び出すサービス操作が含まれます。

コードから GetBlog() を呼び出すには

ベースアドレスと呼び出すメソッドを使用して XmlReader を作成します。

Uri serviceAddress = new Uri("http://localhost:8000/BlogService/GetBlog");

Dim serviceAddress As New Uri("http://localhost:8000/BlogService/GetBlog")

静的な Load(XmlReader) メソッドを呼び出し、作成した XmlReader を渡します。

XmlReader reader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog");
SyndicationFeed feed = SyndicationFeed.Load(reader);

Dim reader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog")
Dim feed As SyndicationFeed = SyndicationFeed.Load(reader)

これにより、サービス操作が呼び出され、サービス操作から返されたフォーマッタが新しい SyndicationFeed に設定されます。

フィードオブジェクトにアクセスします。

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(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

例

この例の完全なコードの一覧を以下に示します。

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

コードのコンパイル

上記のコードのコンパイル時には、System.ServiceModel.dll と System.ServiceModel.Web.dll が参照されます。

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