WCF 上的 DataContract 和层次结构问题答案

【问题标题】：Problem with DataContract and hierarchy on WCFWCF 上的 DataContract 和层次结构问题
【发布时间】：2011-07-26 19:39:31
【问题描述】：

我的 wcf 项目中的一个对象有问题。我可以说这个对象：

[DataContract(Name="ClassA")]
public class Person{
   //---attributes---
}

[DataContract(Name="ClassB")]
public class Men : Person{
  //---attributes---
}

其中 ClassB 是 ClassA 在另一边的子级。然后我有一个方法是 post:

[OperationContract]
[WebInvoke(UriTemplate= "Person", ResponseFormat = WebMessageFormat.Json, Method= "POST")]
public string PostPerson(Person person) {
    if(person is Men){
       //code...
    }
}

问题是我收到了这个人（在另一边，他们将我作为 B 类发送）但这个人是 Men 返回 false.. 为什么？

【问题讨论】：

标签： wcf c#-4.0 datacontract

【解决方案1】：

您需要将[ServiceKnownType(typeof(Men))] 属性添加到 PostPerson 方法。

【讨论】：

【解决方案2】：

正如 Ryan Gross 所提到的，你需要 Men 是一种众所周知的类型。 Here's a similar question/answer here on SO. 链接文章中未提及的一个选项是KnownType attribute。这是我过去使用的代码示例。前提是这个类是你所有数据合约的基类，并且你所有的数据合约都在同一个程序集中：

/// <summary>
///   Base class for all data contracts.
/// </summary>
[DataContract(Name = "Base", Namespace = "your namespace")]
[KnownType("GetKnownTypes")]
public class BaseDC : IExtensibleDataObject
{
  #region Constants and Fields

  /// <summary>
  ///   Instance used to control access to the known types list.
  /// </summary>
  private static readonly object _knownTypesLock = new object();

  /// <summary>
  ///   Classes derived from this class.  Needed to ensure proper functioning of the WCF data
  ///   constract serializer.
  /// </summary>
  private static List<Type> _knownTypes;

  #endregion

  #region Properties

  /// <summary>
  ///   Gets or sets an <c>ExtensionDataObject</c> that contains data that is not recognized as belonging to the
  ///   data contract.
  /// </summary>
  public ExtensionDataObject ExtensionData { get; set; }

  #endregion

  #region Public Methods

  /// <summary>
  ///   Enumerates the types in the assembly containing <c>BaseDC</c> that derive from <c>BaseDC</c>.
  /// </summary>
  /// <returns>List of <c>BaseDC</c>-derived types.</returns>
  [SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate",
    Justification = "Not appropriate for a property.")]
  public static IEnumerable<Type> GetKnownTypes()
  {
    lock (_knownTypesLock)
    {
      if (_knownTypes == null)
      {
        _knownTypes = new List<Type>();
        Assembly contractsAssembly = Assembly.GetAssembly(typeof(BaseDC));
        Type[] assemblyTypes = contractsAssembly.GetTypes();
        foreach (Type assemblyType in assemblyTypes)
        {
          if (assemblyType.IsClass && !assemblyType.IsGenericType)
          {
            if (assemblyType.IsSubclassOf(typeof(BaseDC)))
            {
              _knownTypes.Add(assemblyType);
            }
          }
        }

        _knownTypes.Add(typeof(BaseDC));
      }

      return _knownTypes;
    }
  }

  #endregion
}

【讨论】：