谈谈WCF中的Data Contract（3）：WCF Data Contract对Collection & Dictionary的支持

Data Contract for Collection

我们照例用例子来说明问题，在这里我们创建一个批量处理Order的Service，于是我们创建了一个OrderCollection Type:

namespace Artech.SpecialDataContract.Contract
{
    [DataContract]
    public class Order
    {
        [DataMember]
        public Guid OrderID
        { get; set; }

        [DataMember]
        public DateTime OrderDate
        { get; set; }
    }

    public class OrderCollection : List<Order>
    {

    }
}

下面是Service Contract的定义：

namespace Artech.SpecialDataContract.Contract
{
    [ServiceContract]
    public interface IOrderManager
    {
        [OperationContract(Name = "ProcessWithCollection")]
        void Process(OrderCollection orders);
}

面是OrderCollection 在XSD中的呈现：

<? xml version="1.0" encoding="utf-8"  ?>
< xs:schema  elementFormDefault ="qualified"  targetNamespace ="http://schemas.datacontract.org/2004/07/Artech.SpecialDataContract.Contract"
    xmlns:xs ="http://www.w3.org/2001/XMLSchema"  xmlns:tns ="http://schemas.datacontract.org/2004/07/Artech.SpecialDataContract.Contract"
    xmlns:ser ="http://schemas.microsoft.com/2003/10/Serialization/" >
   < xs:import  schemaLocation ="http://artech/Artech.SpecialDataContract/OrderManagerService.svc?xsd=xsd1"
          namespace ="http://schemas.microsoft.com/2003/10/Serialization/"   />
   < xs:complexType  name ="ArrayOfOrder" >
     < xs:sequence >
       < xs:element  minOccurs ="0"  maxOccurs ="unbounded"  name ="Order"  nillable ="true"  type ="tns:Order"   />
     </ xs:sequence >
   </ xs:complexType >
   < xs:element  name ="ArrayOfOrder"  nillable ="true"  type ="tns:ArrayOfOrder" />
   < xs:complexType
name ="Order" >
     < xs:sequence >
       < xs:element  minOccurs ="0"  name ="OrderDate"  type ="xs:dateTime" />
       < xs:element
minOccurs ="0"  name ="OrderID"  type ="ser:guid" />
     </ xs:sequence >
   </ xs:complexType >
   < xs:element
name ="Order"  nillable ="true"  type ="tns:Order" />
</ xs:schema >

加上通过Add Service Reference默认生成的Class，我们可以很清楚地看出Collection是以Array的形式呈现的（Artech.SpecialDataContract.Client.OrderManagerService.Order[] orders）：

    [System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "3.0.0.0")]
    [System.ServiceModel.ServiceContractAttribute(ConfigurationName="OrderManagerService.IOrderManager")]
     public  interface IOrderManager  { 
        [System.ServiceModel.OperationContractAttribute(Action="http://tempuri.org/IOrderManager/ProcessWithCollection", ReplyAction="http://tempuri.org/IOrderManager/ProcessWithCollectionResponse")]
        void ProcessWithCollection(Artech.SpecialDataContract.Client.OrderManagerService.Order[] orders);
}

因为Array相对很Common的数据类型，基本上所有的厂商均提供了对Array的支持，这也是WCF在通过Add Service Reference生成Client端代码的时候，会生成Array的原因。不过并不是我们只有唯一的选择，事实上VS为此提供了扩展，允许我们对于基于Collection 的Data Contract生成我们需要的各种类型，我们只需要在Add Service Reference的时候选择“Configure Service Reference”进行相应的配置：

通过上面的截图，我们发现在Collection Type一项我们有若干选项，我们可以选择我们希望生成的数据类型：Array，ArrayList，LinkedList，Generic List，Collection和BindingList。 

Data Contract for Dictionary

前面的内容，我们分别讨论了基于Generic和Collection的Data Contract，接下来，我们来讨论最后一个特殊的数据类型的Data Contract：Dictionary。

延续上面的Order Batch Processing的例子，不过我们现在处理的不是一个OrderCollection对象，而是一个Dictionary对象，线面是Service Contract和Order的定义：

namespace Artech.SpecialDataContract.Contract
{
    [ServiceContract]
    public interface IOrderManager
    {
        [OperationContract(Name = "ProcessWithCollection")]
        void Process(OrderCollection orders);

        [OperationContract(Name = "ProcessWithDictionary")]
        void Process(IDictionary<Guid, Order> orders);
    }
}

    [DataContract]
     public  class Order
     {
        [DataMember]
        public Guid OrderID
        { get; set; }

        [DataMember]
        public DateTime OrderDate
        { get; set; }
    }

闲话少说，我们来看XSD：

<? xml version="1.0" encoding="utf-8" ?>
< xs:schema  elementFormDefault ="qualified"  targetNamespace ="http://schemas.microsoft.com/2003/10/Serialization/Arrays"  xmlns:xs ="http://www.w3.org/2001/XMLSchema"  xmlns:tns ="http://schemas.microsoft.com/2003/10/Serialization/Arrays"  xmlns:ser ="http://schemas.microsoft.com/2003/10/Serialization/" >
   < xs:import  schemaLocation ="http://artech/Artech.SpecialDataContract/OrderManagerService.svc?xsd=xsd1"  namespace ="http://schemas.microsoft.com/2003/10/Serialization/" />
   < xs:import  schemaLocation ="http://artech/Artech.SpecialDataContract/OrderManagerService.svc?xsd=xsd2"  namespace ="http://schemas.datacontract.org/2004/07/Artech.SpecialDataContract.Contract" />
   < xs:complexType  name ="ArrayOfKeyValueOfguidOrder_SkVQi6O3" >
     < xs:annotation >
       < xs:appinfo >
         < IsDictionary  xmlns ="http://schemas.microsoft.com/2003/10/Serialization/" >true </ IsDictionary >
       </ xs:appinfo >
     </ xs:annotation >
     < xs:sequence >
       < xs:element  minOccurs ="0"  maxOccurs ="unbounded"  name ="KeyValueOfguidOrder_SkVQi6O3" >
         < xs:complexType >
           < xs:sequence >
             < xs:element  name ="Key"  type ="ser:guid" />
             < xs:element  name ="Value"  nillable ="true"  type ="q1:Order"  xmlns:q1 ="http://schemas.datacontract.org/2004/07/Artech.SpecialDataContract.Contract" />
           </ xs:sequence >
         </ xs:complexType >
       </ xs:element >
     </ xs:sequence >
   </ xs:complexType >
   < xs:element  name ="ArrayOfKeyValueOfguidOrder_SkVQi6O3"  nillable ="true"  type ="tns:ArrayOfKeyValueOfguidOrder_SkVQi6O3" />
</ xs:schema >

Data Contract的名称为ArrayOfKeyValueOfguidOrder_SkVQi6O3=ArrayOfKeyValueOf+guid（Key的类型）+Order（Value）+_SkVQi6O3（Hash Value）。从该XSD的结构我们不难看出，只是一个数组，每个元素为Key-Value pair。

我们照例看看通过Add Service Reference方式生成的Client端code中的对应的定义：

    [System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "3.0.0.0")]
    [System.ServiceModel.ServiceContractAttribute(ConfigurationName="OrderManagerService.IOrderManager")]
     public  interface IOrderManager  {               
        [System.ServiceModel.OperationContractAttribute(Action="http://tempuri.org/IOrderManager/ProcessWithDictionary", ReplyAction="http://tempuri.org/IOrderManager/ProcessWithDictionaryResponse")]
        void ProcessWithDictionary(System.Collections.Generic.Dictionary<System.Guid, Artech.SpecialDataContract.Client.OrderManagerService.Order> orders);
    }

生成的是一个System.Collections.Generic.Dictionary类型。同Collection一样，也依然可以有多种选择：

[原创]谈谈WCF中的Data Contract（1）：Data Contract Overview
[原创]谈谈WCF中的Data Contract（2）：WCF Data Contract对Generic的支持
[原创]谈谈WCF中的Data Contract（3）：WCF Data Contract对Collection & Dictionary的支持
[原创]谈谈WCF中的Data Contract（4）：WCF Data Contract Versioning