哈希表如何在WCF中工作？

Question

我有问题。

考虑下面

IService1.cs

[ServiceContract] 
public interface IService1 
{ 


    [OperationContract] 
    Hashtable GetHashTableCollection(); 


    [OperationContract] 
    List<A> GetARecords(); 


} 

[DataContract] 
public class A 
{ 
    [DataMember] 
    public int MyProperty { get; set; } 

    [DataMember] 
    public Hashtable MyTable { get; set; } 
} 

Service1.cs

public class Service1 : IService1 
    { 
     public Hashtable GetHashTableCollection() 
     { 
      Hashtable hashtable = new Hashtable(); 
      hashtable.Add("Area", 1000); 
      hashtable.Add("Perimeter", 55); 
      hashtable.Add("Mortgage", 540); 
      return hashtable; 
     } 

     public List<A> GetARecords() 
     { 
      List<A> Alist = new List<A>(); 
      Alist.Add(new A { MyProperty = 1, MyTable = GetHashTableCollection() }); 
      Alist.Add(new A { MyProperty = 2, MyTable = GetHashTableCollection() }); 

      return Alist; 
     } 
    } 

和客户机应用是作为下

private void button1_Click(object sender, EventArgs e) 
{ 
    ServiceReference1.Service1Client sc = new ServiceReference1.Service1Client(); 
    var r1 = sc.GetHashTableCollection(); 
    var r2 = sc.GetARecords(); 
} 

它工作正常，没有任何问题。 HashTable已被转换为Dictionary对象。

我的印象是，因为HashTable使用IDictionary，所以它应该在编译时失败（发生在3.5）。

无法隐式转换类型 'System.Collections.Generic.Dictionary' 到 'System.Collections.Hashtable'

但是，它的工作。怎么样？

我是否缺少任何基本概念？或者DataContractSerializer正在做这项工作？或者在dot.net 4.0中改变了一些东西？

它是什么以及它为什么工作？

Answer 1

它基于IDictionary。 WCF将IDictionary视为Dictionary<object, object>，它在WSDL上公开。你可以有一个自定义的类实现IDictionary，并且行为将是相同的。例如，如果您运行以下任一项目，并使用svcutil或添加服务引用来为该服务生成代理（您有IDictionary类型），则您将在客户端中获得Dictionary<object, object>。

public class StackOverflow_15471185 
{ 
    [ServiceContract] 
    public interface IService1 
    { 
     [OperationContract] 
     Hashtable GetHashTableCollection(); 
     [OperationContract] 
     List<A> GetARecords(); 
    } 

    [DataContract] 
    public class A 
    { 
     [DataMember] 
     public int MyProperty { get; set; } 

     [DataMember] 
     public Hashtable MyTable { get; set; } 
    } 

    public class Service : IService1 
    { 
     public Hashtable GetHashTableCollection() 
     { 
      Hashtable hashtable = new Hashtable(); 
      hashtable.Add("Area", 1000); 
      hashtable.Add("Perimeter", 55); 
      hashtable.Add("Mortgage", 540); 
      return hashtable; 

     } 

     public List<A> GetARecords() 
     { 
      List<A> Alist = new List<A>(); 
      Alist.Add(new A { MyProperty = 1, MyTable = GetHashTableCollection() }); 
      Alist.Add(new A { MyProperty = 2, MyTable = GetHashTableCollection() }); 

      return Alist; 
     } 
    } 

    public static void Test() 
    { 
     string baseAddress = "http://" + Environment.MachineName + ":8000/Service"; 
     ServiceHost host = new ServiceHost(typeof(Service), new Uri(baseAddress)); 
     host.AddServiceEndpoint(typeof(IService1), new BasicHttpBinding(), ""); 
     host.Description.Behaviors.Add(new ServiceMetadataBehavior { HttpGetEnabled = true }); 
     host.Open(); 
     Console.WriteLine("Host opened"); 

     var factory = new ChannelFactory<IService1>(new BasicHttpBinding(), new EndpointAddress(baseAddress)); 
     var proxy = factory.CreateChannel(); 
     Console.WriteLine(proxy.GetHashTableCollection()); 

     ((IClientChannel)proxy).Close(); 
     factory.Close(); 

     Console.Write("Press ENTER to close the host"); 
     Console.ReadLine(); 
     host.Close(); 
    } 
} 

public class StackOverflow_15471185_b 
{ 
    [ServiceContract] 
    public interface IService1 
    { 
     [OperationContract] 
     MyDic GetHashTableCollection(); 
     [OperationContract] 
     List<A> GetARecords(); 
    } 

    public class MyDic : IDictionary 
    { 
     public IDictionary dic = new Hashtable(); 

     public void Add(object key, object value) 
     { 
      dic.Add(key, value); 
     } 

     public void Clear() 
     { 
      dic.Clear(); 
     } 

     public bool Contains(object key) 
     { 
      return dic.Contains(key); 
     } 

     public IDictionaryEnumerator GetEnumerator() 
     { 
      return dic.GetEnumerator(); 
     } 

     public bool IsFixedSize 
     { 
      get { return dic.IsFixedSize; } 
     } 

     public bool IsReadOnly 
     { 
      get { return dic.IsReadOnly; } 
     } 

     public ICollection Keys 
     { 
      get { return dic.Keys; } 
     } 

     public void Remove(object key) 
     { 
      dic.Remove(key); 
     } 

     public ICollection Values 
     { 
      get { return dic.Values; } 
     } 

     public object this[object key] 
     { 
      get 
      { 
       return dic[key]; 
      } 
      set 
      { 
       dic[key] = value; 
      } 
     } 

     public void CopyTo(Array array, int index) 
     { 
      dic.CopyTo(array, index); 
     } 

     public int Count 
     { 
      get { return dic.Count; } 
     } 

     public bool IsSynchronized 
     { 
      get { return dic.IsSynchronized; } 
     } 

     public object SyncRoot 
     { 
      get { return dic.SyncRoot; } 
     } 

     IEnumerator IEnumerable.GetEnumerator() 
     { 
      return ((IEnumerable)dic).GetEnumerator(); 
     } 
    } 

    [DataContract] 
    public class A 
    { 
     [DataMember] 
     public int MyProperty { get; set; } 

     [DataMember] 
     public MyDic MyTable { get; set; } 
    } 

    public class Service : IService1 
    { 
     public MyDic GetHashTableCollection() 
     { 
      MyDic hashtable = new MyDic(); 
      hashtable.Add("Area", 1000); 
      hashtable.Add("Perimeter", 55); 
      hashtable.Add("Mortgage", 540); 
      return hashtable; 

     } 

     public List<A> GetARecords() 
     { 
      List<A> Alist = new List<A>(); 
      Alist.Add(new A { MyProperty = 1, MyTable = GetHashTableCollection() }); 
      Alist.Add(new A { MyProperty = 2, MyTable = GetHashTableCollection() }); 

      return Alist; 
     } 
    } 

    public static void Test() 
    { 
     string baseAddress = "http://" + Environment.MachineName + ":8000/Service"; 
     ServiceHost host = new ServiceHost(typeof(Service), new Uri(baseAddress)); 
     host.AddServiceEndpoint(typeof(IService1), new BasicHttpBinding(), ""); 
     host.Description.Behaviors.Add(new ServiceMetadataBehavior { HttpGetEnabled = true }); 
     host.Open(); 
     Console.WriteLine("Host opened"); 

     var factory = new ChannelFactory<IService1>(new BasicHttpBinding(), new EndpointAddress(baseAddress)); 
     var proxy = factory.CreateChannel(); 
     Console.WriteLine(proxy.GetHashTableCollection()); 

     ((IClientChannel)proxy).Close(); 
     factory.Close(); 

     Console.Write("Press ENTER to close the host"); 
     Console.ReadLine(); 
     host.Close(); 
    } 
}