DataContract, default DataMember value

问题:

Is there a way to choose default values of attributes that are not in the xml file during deserialization?
If the mAge attribute is not present in the xml file, I want to use a default value of 18. Is it possible ?

[DataContract]
public class Person 
{
    public Person ()
    {
    }
    [DataMember(Name = "Name")]
    public string mName { get; set; }
    [DataMember(Name = "Age")]
    public int mAge { get; set; }
    [DataMember(Name = "Single")]
    public bool mIsSingle { get; set; }
};

Edit to put the answer.

[DataContract]
public class Person 
{
    public Person ()
    {
    }
    [DataMember(Name = "Name")]
    public string mName { get; set; }
    [DataMember(Name = "Age")]
    public int? mAge { get; set; }
    [DataMember(Name = "Single")]
    public bool? mIsSingle { get; set; }

    [System.Runtime.Serialization.OnDeserialized]
    void OnDeserialized(System.Runtime.Serialization.StreamingContext c)
    {
        mAge = (mAge == null ? 18 : mAge); // 18 is the default value
    }
}

回答1:

You can use [OnDeserialized]

Use the OnDeserializedAttribute when you need to fix values on a deserialized object after it has been deserialized and before the graph is returned.

[DataContract]
 public class Person 
  {
    public Person ()
    {
    }
    [DataMember(Name = "Name")]
    public string mName { get; set; }
    [DataMember(Name = "Age")]
    public int mAge { get; set; }
    [DataMember(Name = "Single")]
    public bool mIsSingle { get; set; }



    [System.Runtime.Serialization.OnDeserialized]
    void OnDeserialized(System.Runtime.Serialization.StreamingContext c)
    {
      mAge = (mAge == 0) ?18:mAge;
    }
  }
}

EDIT: From your Comments

For bool or int you can use nullable bool and nullable int so if these age and Single attributes are missing in xml file then they will be null as well.

here is quick sample I prepared

using System.Runtime.Serialization;
using System.ServiceModel;
using MySpace;
using System.ServiceModel.Channels;
using System;
namespace MySpace
{

 [DataContract]
 public class Person 
  {
    public Person ()
    {
    }
    [DataMember(Name = "Name")]
    public string mName { get; set; }
    [DataMember(Name = "Age")]
    public int? mAge { get; set; }
    [DataMember(Name = "Single")]
    public bool? mIsSingle { get; set; }



    [System.Runtime.Serialization.OnDeserialized]
    void OnDeserialized(System.Runtime.Serialization.StreamingContext c)
    {
      mAge =  (mAge == null ? 18 : mAge);
    }
  }
}
[ServiceContract]
public interface IService
{
  [OperationContract]
  Person Method(Person dd);
}

public class Service : IService
{
  public Person Method(Person dd)
  {
    return dd;
  }
}

class Program
{
  static void Main(string[] args)
  {
    string Url = "http://localhost:8000/";
    Binding binding = new BasicHttpBinding();
    ServiceHost host = new ServiceHost(typeof(Service));
    host.AddServiceEndpoint(typeof(IService), binding, Url);
    host.Open();
    ChannelFactory<IService> fac = new ChannelFactory<IService>(binding);
    fac.Open();
    IService proxy = fac.CreateChannel(new EndpointAddress(Url));
    Person d = new Person();
    d.mName = "BuzBuza";

    Console.WriteLine("Data before calling service " + (d.mAge == null ? " null " : d.mAge.Value.ToString()));
    Console.WriteLine("Data before calling service " + (d.mIsSingle == null ? "null" : d.mIsSingle.Value.ToString()));
    d = proxy.Method(d);
    fac.Close();
    host.Close();
    Console.WriteLine("Data after calling service " + (d.mAge == null ? " null " : d.mAge.Value.ToString()));
    Console.WriteLine("Data after calling service " + (d.mIsSingle == null ? "null" : d.mIsSingle.Value.ToString()));

    Console.ReadLine();
  }
}

回答2:

use [OnDeserializing()]

and you set your values BEFORE the deserialization. So there is no check necessary, which could go wrong - what if the mAge was serialized to be 0?

回答3:

This should work.

[DataContract]
 public class Person 
  {
    public Person ()
    {
    }
    [DataMember(Name = "Name")]
    public string mName { get; set; }
    [DataMember(Name = "Age")]
    public int mAge = 18;
    [DataMember(Name = "Single")]
    public bool mIsSingle { get; set; }
  };

Take a look at this page.