.net 在 WCF 中，数据协定类可以相互继承吗？

In WCF, can data contract classes inherit from one another?

提问by Jordan Parmer

In a WCF service, I have two classes with the [DataContract] attribute. One of these classes has an "is-a" relationship with the other - so class B can inherit from class A. However, when I configure inheritance between these two classes, both denoted with a [DataContract] attribute, the metadata fails to load when testing the services.

在 WCF 服务中，我有两个具有 [DataContract] 属性的类。其中一个类与另一个类具有“is-a”关系 - 因此类 B 可以从类 A 继承。但是，当我在这两个类之间配置继承时，都用 [DataContract] 属性表示，元数据无法加载在测试服务时。

Is this possible in WCF? Am I missing another attribute?

这在 WCF 中可能吗？我是否缺少另一个属性？

[DataContract]
public class A
{        
    [DataMember]
    public MyCustomType AValue1{ get; set; }

    [DataMember]
    public MyCustomType AValue2 { get; set; }
}

[DataContract]
public class B: A
{       
   [DataMember]
   public double BValue1{ get; set; }

   [DataMember]
   public double BValue2 { get; set; }
}

NOTE: The custom types are also defined using data contracts.

注意：自定义类型也是使用数据协定定义的。

UPDATE: Below is the error:

更新：以下是错误：

Error: Cannot obtain Metadata from http://localhost:8002/GISDataServices/mexIf this is a Windows (R) Communication Foundation service to which you have access, please check that you have enabled metadata publishing at the specified address. For help enabling metadata publishing, please refer to the MSDN documentation at http://go.microsoft.com/fwlink/?LinkId=65455.WS-MetadataExchange Error URI: http://localhost:8002/GISDataServices/mexMetadata contains a reference that cannot be resolved: 'http://localhost:8002/GISDataServices/mex'. Receivera:InternalServiceFaultThe server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the <serviceDebug> configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework 3.0 SDK documentation and inspect the server trace logs.HTTP GET Error URI: http://localhost:8002/GISDataServices/mexThere was an error downloading 'http://localhost:8002/GISDataServices/mex'. The request failed with HTTP status 400: Bad Request.

错误：无法从http://localhost:8002/GISDataServices/mex获取元数据如果这是您有权访问的 Windows (R) Communication Foundation 服务，请检查您是否已在指定地址启用元数据发布。有关启用元数据发布的帮助，请参阅 MSDN 文档，网址为http://go.microsoft.com/fwlink/?LinkId=65455.WS-MetadataExchange Error URI: http://localhost:8002/GISDataServices/mexMetadata contains无法解析的引用：“ http://localhost:8002/GISDataServices/mex”。 Receivera:InternalServiceFault由于内部错误，服务器无法处理请求。有关错误的详细信息，请在服务器上打开 IncludeExceptionDetailInFaults（从 ServiceBehaviorAttribute 或从 <serviceDebug> 配置行为），以便将异常信息发送回客户端，或者根据 Microsoft .NET Framework 打开跟踪3.0 SDK 文档并检查服务器跟踪日志。HTTP GET 错误 URI：http://localhost:8002/GISDataServices/mex下载“ http://localhost:8002/GISDataServices/mex”时出错。请求失败，HTTP 状态为 400：错误请求。

UPDATE 2:See my answer below.

更新 2：见下面我的回答。

回答by David Morton

Yes, but you need to decorate the base class with the [KnownTypeAttribute] constructing it with the derived class's type. For instance:

是的，但是您需要使用 [KnownTypeAttribute] 来装饰基类，并使用派生类的类型构造它。例如：

[DataContract]
[KnownType(typeof(B))]
public class A
{
   [DataMember]
   public string Value { get; set; }
}

[DataContract]
public class B : A
{
   [DataMember]
   public string OtherValue { get; set; }
}

回答by Jordan Parmer

Okay, I figured out the question. The answer is...I'm an idiot. It had nothing to do with inheritance. In the base class, I had a data contract member without a 'set' property clause - only a 'get'. Doh!!! Putting in a 'set' clause made it work like a charm.

好的，我想通了这个问题。答案是……我是个白痴。它与继承无关。在基类中，我有一个没有“set”属性条款的数据契约成员——只有一个“get”。啊！！！放入一个“set”子句使它像魅力一样工作。

Sorry for the confusion.

对困惑感到抱歉。

回答by bendewey

Based on this test it should work fine. Do both classes have Default Constructors? Are you using Auto-Properties. Note, In this basic sample the Attributes aren't required. Also, as David Morton mentioned you depending on which element you're returning you may need the KnownType attribute, I'm not 100% but the known type might have to go on the operation contract.

基于此测试，它应该可以正常工作。两个类都有默认构造函数吗？您是否在使用自动属性。注意，在这个基本示例中，不需要属性。此外，正如 David Morton 提到的，根据您返回的元素，您可能需要 knownType 属性，我不是 100% 但已知类型可能必须符合操作合同。

class Program
{
    static void Main(string[] args)
    {
        var serializer = new DataContractSerializer(typeof(Employee));

        var employee = new Employee() { Name="Joe", Salary=100000  };
        using (var ms = new MemoryStream())
        {
            serializer.WriteObject(ms, employee);

            ms.Position = 0;

            var newEmployee = serializer.ReadObject(ms) as Employee;
        }

        Console.ReadKey();

    }
}

[DataContract]
public class Employee : Person
{
    [DataMember]
    public decimal Salary { get; set; }
}

[DataContract]
public class Person
{
    [DataMember]
    public string Name { get; set; }
}

[ServiceContract]
interface IEmployeeService
{
    [OperationContract]
    Person GetPerson();

    [OperationContract]
    Employee GetEmployee();

    [OperationContract]
    [KnownType(typeof(Employee))]
    Person GetEmployeeAsPerson();
}