如何使用 WCF DataContracts 自动反序列化 Yahoo GeoPlanet REST XML

Question

我是 WCF 的新手。我能够成功地为 GeoNames 服务创建客户端，但现在我正在尝试为 Yahoo GeoPlanet 做同样的事情，我似乎无法让 XML 反序列化为我的 DataContract 类型。这样做的正确方法是什么？这是我正在使用的：

示例 REST 响应：

<places xmlns="http://where.yahooapis.com/v1/schema.rng" 
    xmlns:yahoo="http://www.yahooapis.com/v1/base.rng" 
    yahoo:start="0" yahoo:count="247" yahoo:total="247">
    <place yahoo:uri="http://where.yahooapis.com/v1/place/23424966" 
        xml:lang="en-US">
        <woeid>23424966</woeid>
        <placeTypeName code="12">Country</placeTypeName>
        <name>Sao Tome and Principe</name>
    </place>
    <place yahoo:uri="http://where.yahooapis.com/v1/place/23424824" 
        xml:lang="en-US">
        <woeid>23424824</woeid>
        <placeTypeName code="12">Country</placeTypeName>
        <name>Ghana</name>
    </place>
    ...
</places>

合约界面和客户端：

[ServiceContract]
public interface IConsumeGeoPlanet
{
    [OperationContract]
    [WebGet(
        UriTemplate = "countries?appid={appId}",
        ResponseFormat = WebMessageFormat.Xml,
        BodyStyle = WebMessageBodyStyle.Bare
    )]
    GeoPlanetResults<GeoPlanetPlace> Countries(string appId);
}

public sealed class GeoPlanetConsumer : ClientBase<IConsumeGeoPlanet>
{
    public GeoPlanetResults<GeoPlanetPlace> Countries(string appId)
    {
        return Channel.Countries(appId);
    }
}

反序列化类型：

[DataContract(Name = "places", 
    Namespace = "http://where.yahooapis.com/v1/schema.rng")]
public sealed class GeoPlanetResults<T> : IEnumerable<T>
{
    public List<T> Items { get; set; }

    public IEnumerator<T> GetEnumerator()
    {
        return Items.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}


[DataContract]
public class GeoPlanetPlace
{
    [DataMember(Name = "woeid")]
    public int WoeId { get; set; }

    [DataMember(Name = "placeTypeName")]
    public string Type { get; set; }

    [DataMember(Name = "name")]
    public string Name { get; set; }

}

我知道这是错误的。在我的 geonames 客户端中，我的 GeoNamesResults 类有一个没有属性的 [DataContract] 属性，以及 Items 属性上的一个 [DataMember(Name = "geonames")] 属性。不过，这对 GeoPlanet 不起作用，我不断收到反序列化异常。我可以让Countries(appId) 方法毫无例外地执行的唯一方法是将Name 和Namespace 放在DataContract 属性中。但是，当我这样做时，我不知道如何将结果反序列化到 Items 集合中（它为空）。

我该怎么办？

Answer 1

DataContractSerializer 不支持完整的 XML 规范，仅支持其中的一个子集。它不支持的是属性，它在您显示的示例响应中被广泛使用。在这种情况下，您需要使用XmlSerializer，并相应地定义类型（使用System.Xml.Serialization 中的属性，而不是System.Runtime.Serialization 中的属性）。下面的代码显示了如何检索您发布的示例 XML。

public class StackOverflow_8022154
{
    const string XML = @"<places xmlns=""http://where.yahooapis.com/v1/schema.rng""  
    xmlns:yahoo=""http://www.yahooapis.com/v1/base.rng""  
    yahoo:start=""0"" yahoo:count=""247"" yahoo:total=""247""> 
    <place yahoo:uri=""http://where.yahooapis.com/v1/place/23424966""  
        xml:lang=""en-US""> 
        <woeid>23424966</woeid> 
        <placeTypeName code=""12"">Country</placeTypeName> 
        <name>Sao Tome and Principe</name> 
    </place> 
    <place yahoo:uri=""http://where.yahooapis.com/v1/place/23424824""  
        xml:lang=""en-US""> 
        <woeid>23424824</woeid> 
        <placeTypeName code=""12"">Country</placeTypeName> 
        <name>Ghana</name> 
    </place> 
</places>";

    const string ElementsNamespace = "http://where.yahooapis.com/v1/schema.rng";
    const string YahooNamespace = "http://www.yahooapis.com/v1/base.rng";
    const string XmlNamespace = "http://www.w3.org/XML/1998/namespace";

    [XmlType(Namespace = ElementsNamespace, TypeName = "places")]
    [XmlRoot(ElementName = "places", Namespace = ElementsNamespace)]
    public class Places
    {
        [XmlAttribute(AttributeName = "start", Namespace = YahooNamespace)]
        public int Start { get; set; }
        [XmlAttribute(AttributeName = "count", Namespace = YahooNamespace)]
        public int Count;
        [XmlAttribute(AttributeName = "total", Namespace = YahooNamespace)]
        public int Total;
        [XmlElement(ElementName = "place", Namespace = ElementsNamespace)]
        public List<Place> AllPlaces { get; set; }

        public override string ToString()
        {
            StringBuilder sb = new StringBuilder();
            sb.AppendFormat("Places[start={0},count={1},total={2}]:", this.Start, this.Count, this.Total);
            sb.AppendLine();
            foreach (var place in this.AllPlaces)
            {
                sb.AppendLine("   " + place.ToString());
            }

            return sb.ToString();
        }
    }
    [XmlType(TypeName = "place", Namespace = ElementsNamespace)]
    public class Place
    {
        [XmlAttribute(AttributeName = "uri", Namespace = YahooNamespace)]
        public string Uri { get; set; }
        [XmlAttribute(AttributeName = "lang", Namespace = XmlNamespace)]
        public string Lang { get; set; }
        [XmlElement(ElementName = "woeid")]
        public string Woeid { get; set; }
        [XmlElement(ElementName = "placeTypeName")]
        public PlaceTypeName PlaceTypeName;
        [XmlElement(ElementName = "name")]
        public string Name { get; set; }

        public override string ToString()
        {
            return string.Format("Place[Uri={0},Lang={1},Woeid={2},PlaceTypeName={3},Name={4}]",
                this.Uri, this.Lang, this.Woeid, this.PlaceTypeName, this.Name);
        }
    }
    [XmlType(TypeName = "placeTypeName", Namespace = ElementsNamespace)]
    public class PlaceTypeName
    {
        [XmlAttribute(AttributeName = "code")]
        public string Code { get; set; }
        [XmlText]
        public string Value { get; set; }

        public override string ToString()
        {
            return string.Format("TypeName[Code={0},Value={1}]", this.Code, this.Value);
        }
    }
    [ServiceContract]
    public interface IConsumeGeoPlanet
    {
        [OperationContract]
        [WebGet(
            UriTemplate = "countries?appid={appId}",
            ResponseFormat = WebMessageFormat.Xml,
            BodyStyle = WebMessageBodyStyle.Bare
        )]
        [XmlSerializerFormat]
        Places Countries(string appId);
    }

    public sealed class GeoPlanetConsumer : ClientBase<IConsumeGeoPlanet>
    {
        public GeoPlanetConsumer(string address)
            : base(new WebHttpBinding(), new EndpointAddress(address))
        {
            this.Endpoint.Behaviors.Add(new WebHttpBehavior());
        }

        public Places Countries(string appId)
        {
            return Channel.Countries(appId);
        }
    }

    [ServiceContract]
    public class SimulatedYahooService
    {
        [WebGet(UriTemplate = "*")]
        public Stream GetData()
        {
            WebOperationContext.Current.OutgoingResponse.ContentType = "text/xml";
            return new MemoryStream(Encoding.UTF8.GetBytes(XML));
        }
    }

    public static void Test()
    {
        Console.WriteLine("First a simpler test with serialization only.");
        XmlSerializer xs = new XmlSerializer(typeof(Places));
        MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(XML));
        object o = xs.Deserialize(ms);
        Console.WriteLine(o);

        Console.WriteLine();
        Console.WriteLine("Now in a real service");
        Console.WriteLine();
        string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
        WebServiceHost host = new WebServiceHost(typeof(SimulatedYahooService), new Uri(baseAddress));
        host.Open();
        Console.WriteLine("Host opened");

        GeoPlanetConsumer consumer = new GeoPlanetConsumer(baseAddress);
        Places places = consumer.Countries("abcdef");
        Console.WriteLine(places);
    }
}