WCF 第六章编码与序列化使用NetDataContractSerializer共享类型

2010-12-20 17:33 DanielWise 阅读(1108) 评论(1) 编辑收藏举报

WCF 中的默认序列化方法是DataContractSerializer. 这是WCF开发组想要大部分开发人员使用的序列化方法因为它强制进行契约共享而非类型共享。这是创建面向服务架构的一个原则。然而，如果你的想法是支持类型一致并在客户端和服务端间共享类型信息那么这个方法并不会为你的设计引入问题，你可以使用NetDataContractSerializer来序列化。就像在之前的”比较WCF序列化选项”章节描述的那样，NetDataContractSerializer与DataContractSerializer本质是类似的，但是额外支持了类型信息共享和引用保留。

尽管WCF支持NetDataContractSerializer，在你的数据契约中没有任何属性来支持使用这个序列化方法。这是为了防止类型共享很轻易的扩散的目的而完成的。为了使用NetDataContractSerializer，你必须使用一个自定义行为(列表6.18)并标识你的操作契约(列表6.19)。

列表6.18 使用NetDataContractFormatAttribute

public class NetDataContractFormatAttribute : Attribute, IOperationBehavior
   {
       public void AddBindingParameters(OperationDescription operationDescription, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
       {
       }
 
       public void ApplyClientBehavior(OperationDescription operationDescription, System.ServiceModel.Dispatcher.ClientOperation clientOperation)
       {
           ReplaceDataContractSerializerOperationBehavior(operationDescription);
       }
 
       public void ApplyDispatchBehavior(OperationDescription operationDescription, System.ServiceModel.Dispatcher.DispatchOperation dispatchOperation)
       {
           ReplaceDataContractSerializerOperationBehavior(operationDescription);
       }
 
       public void Validate(OperationDescription operationDescription)
       {
       }
 
       private static void ReplaceDataContractSerializerOperationBehavior(OperationDescription description)
       {
           DataContractSerializerOperationBehavior dcs = description.Behaviors.Find<DataContractSerializerOperationBehavior>();
           if (dcs != null)
           {
               description.Behaviors.Remove(dcs);
           }
           description.Behaviors.Add(new NetDataContractSerializerOperationBehavior(description));
       }
   }
 
   public class NetDataContractSerializerOperationBehavior : DataContractSerializerOperationBehavior
   {
       private static NetDataContractSerializer serializer = new NetDataContractSerializer();
 
       public NetDataContractSerializerOperationBehavior(OperationDescription description) :
           base(description)
       {
       }
 
       public override XmlObjectSerializer CreateSerializer(Type type,
           string name, string ns, IList<Type> knownTypes)
       {
           return NetDataContractSerializerOperationBehavior.serializer;
       }
 
       public override XmlObjectSerializer CreateSerializer(Type type,
           System.Xml.XmlDictionaryString name, System.Xml.XmlDictionaryString ns, IList<Type> knownTypes)
       {
           return NetDataContractSerializerOperationBehavior.serializer;
       }
   }

为了使用NetDataContractSerializer，需要像列表6.19中显示的那样，在一个操作上使用[NetDataContractFormat]属性。

列表6.19 使用NetDataContract 序列化

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
 
namespace EssentialWCF
{
    [ServiceContract]
    public interface IEmployeeInformation
    {
        [OperationContract]
        [NetDataContractFormat]
        List<Employee> GetEmployees();
    }
}