WCF中帶接口類型參數的泛型返回類型

Question

如何在我的WCF REST服務中從OperationContracts返回泛型類型參數中的接口類型？更具體地說，它適用於一個操作，但不適用於當我使用通用接口T添加第二個操作時。

我使用JSON作爲請求和響應格式，提供一個非WCF客戶端來解析所需數據的JSON響應。我沒有使用SOAP或由服務生成的WSDL。

我的服務接口：

[ServiceContract] 
[ServiceKnownType("GetServiceKnownTypes", typeof(ServiceKnownTypesHelper))] 
public interface IMyService 
{ 
    [WebGet(UriTemplate="count")] 
    [OperationContract] 
    IServiceResult<int> GetCount(); 

    [WebGet(UriTemplate="desc")] 
    [OperationContract] 
    IServiceResult<string> GetDescription(); 

    [WebGet(UriTemplate="foo")] 
    [OperationContract] 
    IServiceResult<IFooData> GetFooData(); 

    // Fails when I invoke either method if I uncomment this operation. 
    //[WebGet(UriTemplate="bar")] 
    //[OperationContract] 
    //IServiceResult<IBarData> GetBarData(); 
} 

我離開GetCount()和GetDescription()的例子指出，這兩個通用的結果做工精細，但很明顯，他們是具體類型。即使GetFooData()工作正常，直到我添加第二種方法IServiceResult<T>其中T是一個接口。

GetFooData()和GetBarData()的返回類型不一樣，實現它們的具體類也不一樣。

你可以想像，我已經減少了實施的骨架，因爲我不認爲實行的是問題的心臟：

#region My service implementation 
public class MyService : IMyService 
{ 
    public IServiceResult<int> GetCount() 
    { 
     return new ServiceResult<int>(42); 
    } 
    public IServiceResult<string> GetDescription() 
    { 
     return new ServiceResult<string>("Muffins"); 
    } 
    public IServiceResult<IFooData> GetFooData() 
    { 
     return new ServiceResult<IFooData>(new FooData() { Foo = 99 }); 
    } 
    public IServiceResult<IBarData> GetBarData() 
    { 
     return new ServiceResult<IBarData>(new BarData() { Bar = "Elvis was here" }); 
    } 
} 
#endregion 

#region ServiceKnownTypesHelper.GetServiceKnownTypes(): 
public static class ServiceKnownTypesHelper 
{ 
    private static IList<Type> serviceKnownTypes = new List<Type>() 
     { 
      typeof(FooData), 
      typeof(BarData), 
      typeof(ServiceResult<int>), 
      typeof(ServiceResult<string>), 
      typeof(ServiceResult<IFooData>), 
      typeof(ServiceResult<IBarData>), 
     }; 

    public static IEnumerable<Type> GetServiceKnownTypes(ICustomAttributeProvider paramIgnored) 
    { 
     return serviceKnownTypes; 
    } 
} 
#endregion 

#region IServiceResult<T> and its concrete implementation: 
public interface IServiceResult<T> 
{ 
    IList<string> Errors { get; } 
    T Value { get; set; } 
} 

[DataContract] 
public class ServiceResult<T> : IServiceResult<T> 
{ 
    public ServiceResult(T value) 
    { 
     this.Value = value; 
    } 

    private IList<string> errors = new List<string>(); 

    [DataMember] 
    public IList<string> Errors 
    { 
     get 
     { 
      return this.errors; 
     } 
    } 

    [DataMember] 
    public T Value { get; set; } 
} 
#endregion 

#region IFooData and its concrete implementation: 
public interface IFooData 
{ 
    int Foo { get; set; } 
} 

[DataContract] 
public class FooData: IFooData 
{ 
    [DataMember] 
    public int Foo { get; set; } 
} 
#endregion 

#region IBarData and its concrete implementation: 
public interface IBarData 
{ 
    string Bar { get; set; } 
} 

[DataContract] 
public class BarData: IBarData 
{ 
    [DataMember] 
    public string Bar { get; set; } 
} 
#endregion 

和錯誤消息時，我調用GetBarData()從瀏覽器：

 
Type 'ServiceResult`1[IBarData]' cannot be added to list of known types since 
another type 'ServiceResult`1[IFooData]' with the same data contract name 
'http://schemas.datacontract.org/2004/07/ServiceResultOfanyType' is 
already present. 

錯誤消息的其餘部分是一個紅色的鯡魚約碰撞集合類型List<Test>和Test[]，這是不是這裏的情況。

很明顯，IFooData和IBarData是不一樣的，也沒有實現它們的類。

那麼爲什麼ServiceResult<IFooData>和ServiceResult<IBarData>都解決爲ServiceResultOfanyType？

我錯過了什麼，或者有沒有辦法解決這個問題？

Answer 1

大量的試驗和錯誤後，我終於得到這個工作以最小的變化：

• 我的服務業務現在回到ServiceResult<T>，而不是IServiceResult<T>。實際上，IServiceResult<T>現在完全消失了。

• GetServiceKnownTypes()不再返回ServiceResult<T>的所有變體。我只返回用作T的DataContract。

  #region My service interface 
  [ServiceContract] 
  [ServiceKnownType("GetServiceKnownTypes", typeof(ServiceKnownTypesHelper))] 
  public interface IMyService 
  { 
      [WebGet(UriTemplate="count")] 
      [OperationContract] 
      ServiceResult<int> GetCount(); 
  
      [WebGet(UriTemplate="desc")] 
      [OperationContract] 
      ServiceResult<string> GetDescription(); 
  
      [WebGet(UriTemplate="foo")] 
      [OperationContract] 
      ServiceResult<IFooData> GetFooData(); 
  
      [WebGet(UriTemplate="bar")] 
      [OperationContract] 
      ServiceResult<IBarData> GetBarData(); 
  } 
  #endregion 
  #region My service implementation (minus bodies) 
  public class MyService : IMyService 
  { 
      public ServiceResult<int> GetCount() {} 
      public ServiceResult<string> GetDescription() {} 
      public ServiceResult<IFooData> GetFooData() {} 
      public ServiceResult<IBarData> GetBarData() {} 
  } 
  #endregion 
  #region ServiceKnownTypes 
  // My list of ServiceKnownTypes is now much shorter and simpler. I was feeding the service too much information 
  public static class ServiceKnownTypesHelper 
  { 
      private static IList<Type> serviceKnownTypes = new List<Type>() 
       { 
        typeof(FooData), 
        typeof(BarData), 
        //typeof(ServiceResult<int>), 
        //typeof(ServiceResult<string>), 
        //typeof(ServiceResult<IFooData>), 
        //typeof(ServiceResult<IBarData>), 
       }; 
  
      // Remaining implementation is the same as before 
  } 
  #endregion 
  #region ServiceResult<T> with no interface (it's not used or needed) 
  [DataContract] 
  public class ServiceResult<T> //: IServiceResult<T> 
  { 
      // implementation is the same as before 
  } 
  #endregion 
  

我現在可以調用所有的這些方法，並取回通過它們的接口在ServiceContract提到泛型類型的列表。