WCF学习笔记(三)使用(Service)KnownType标记实现继承、多态特性

1.服务器端：

/// <summary>
    /// 实现IExtensibleDataObject接口，表示这个类的派生类也可以序列化
    /// IsRequired表示该属性是否需要赋值之后才能序列化
    ///
    /// 注意：此类上没有标记KnownType属性，于是在客户端找不到School的派生类
    /// 若是在此类上没有KnownType标记，在契约接口上使用ServiceKnownType标记也是可以的
    /// 当然，ServiceKnownType标记也是可以应用在接口里面的方法上面的
    /// </summary>
    [DataContract(Name = "SchoolEntity", Namespace = "http://schemas.yoyo/zhu")]
    //[KnownType(typeof(Teacher))]
    //[KnownType(typeof(Student))]
    public class School : IExtensibleDataObject
    {
        /// <summary>
        /// 学校编号
        /// </summary>
        [DataMember(Name = "Num", IsRequired = true, Order = 0)]
        public string s_Num { get; set; }
        /// <summary>
        /// 学校名称
        /// </summary>
        [DataMember(Name = "Name", IsRequired = true, Order = 1)]
        public string s_Name { get; set; }
        /// <summary>
        /// 描述
        /// </summary>
        [DataMember(Name = "Description", IsRequired = false, Order = 2)]
        public string s_Description { get; set; }

        private ExtensionDataObject extensionDataObject;

        #region IExtensibleDataObject 成员

        public ExtensionDataObject ExtensionData
        {
            get
            {
                return extensionDataObject;
            }
            set
            {
                extensionDataObject = value;
            }
        }

        #endregion
    }

派生类：

    [DataContract(Namespace = "http://schemas.yoyo/zhu")]
    public class Student : School
    {
        public Student()
        {
            this.s_SchoolDerivedClass = SchoolEnmu.Student;
        }
    }

    [DataContract(Namespace = "http://schemas.yoyo/zhu")]
    public class Teacher : School
    {
        public Teacher()
        {
            this.s_SchoolDerivedClass = SchoolEnmu.Teacher;
        }
    }

2.契约

    [ServiceContract(Name = "IKonwTypeService", Namespace = "http://www.yoyo/zhu")]
    [ServiceKnownType(typeof(Teacher))]
    [ServiceKnownType(typeof(Student))]
    public interface IKonwTypeService
    {
        [OperationContract]
        void AddTeacher(School sc);
        [OperationContract]
        List<School> GetTeacher();
    }

    //这个ServiceBehavior可有可无
    //[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
    public class KonwTypeService : IKonwTypeService
    {
        private static School school;
        #region IKonwTypeService 成员

        public void AddTeacher(School sc)
        {
            school = sc;
        }

        public List<School> GetTeacher()
        {
            List<School> list = new List<School>();
            list.Add(school);
            return list;
        }

        #endregion
    }

3.宿主环境配置：

           ServiceHost host = new ServiceHost(typeof(KonwTypeService));
            host.Open();
            Console.WriteLine("宿主服务已启动!");
            Console.ReadKey();

  <system.serviceModel>
    <services>
      <service name="KonwTypeServices.KonwTypeService" behaviorConfiguration="serviceBehavior">
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:8044"/>
          </baseAddresses>
        </host>
        <endpoint address="KonwTypeService" contract="KonwTypeServices.IKonwTypeService" binding="basicHttpBinding" />
        <endpoint contract="IMetadataExchange" binding="mexHttpBinding" address="mex" />
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="serviceBehavior">
          <serviceMetadata httpGetEnabled="true"/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>

4.客户端（引用服务的方式见WCF学习笔记(二)）

 

5.注意：当ServiceKnownType和KnownType标记都没使用时，可以在配置文件里面添加如下代码，在客户端也能生成其派生类

<system.runtime.serialization>
  <dataContractSerializer>
    <declaredTypes>
      <add type="EntityModel.School, EntityModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
        <knownType type="EntityModel.Student, EntityModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
        <knownType type="EntityModel.Teacher, EntityModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
      </add>
    </declaredTypes>
  </dataContractSerializer>
  </system.runtime.serialization>

 

小结：

KnowType表示：在WCF中一个继承类可以转换成其父类，加上这个标签后，父类也可以转成子类，从而保留多态性。同时，客户端还不会生成子类的相应信息。
ServiceKnowType:当提供的服务中有参数是上面提及的父类，为了把这个父类的派生类带出来，于是需要在接口上面使用ServiceKnowType指定其派生类。当只需要在某个方法上面使用该父类的派生类，就可

以在该方法的上面使用ServiceKnowType指定即可。
在WCF中，继承的接口和类是反映不到客户端的，因此说WCF牺牲了OO的继承和多态的特性。但是这种特性可以使用已知类型的方式弥补。

 

源代码下载地址：http://download.csdn.net/detail/yoyoshaoye/3614453