如何WCF反序列化实例化对象没有调用构造函数？ [英] How does WCF deserialization instantiate objects without calling a constructor?

问题描述

有一些神奇与WCF反序列化回事。它是如何实例化数据契约类型的实例，而无需调用构造函数？

There is some magic going on with WCF deserialization. How does it instantiate an instance of the data contract type without calling its constructor?

例如，考虑这个数据契约：

For example, consider this data contract:

[DataContract]
public sealed class CreateMe
{
   [DataMember] private readonly string _name;
   [DataMember] private readonly int _age;
   private readonly bool _wasConstructorCalled;

   public CreateMe()
   {
      _wasConstructorCalled = true;
   }

   // ... other members here
}

在通过的DataContractSerializer 获取该对象的实例，你会看到领域 _wasConstructorCalled 是假。

When obtaining an instance of this object via DataContractSerializer you will see that the field _wasConstructorCalled is false.

那么，如何WCF做到这一点？这是其他人可以使用过，或者是看不到它离我们的技术？

So, how does WCF do this? Is this a technique that others can use too, or is it hidden away from us?

推荐答案

FormatterServices.GetUninitializedObject（）将创建一个实例，而无需调用构造函数。我用反射并通过一些核心净序列化类的挖掘发现了这个类。

FormatterServices.GetUninitializedObject() will create an instance without calling a constructor. I found this class by using Reflector and digging through some of the core .Net serialization classes.

我测试了它使用下面的示例code，它看起来像它的伟大工程：

I tested it using the sample code below and it looks like it works great:

using System;
using System.Reflection;
using System.Runtime.Serialization;

namespace NoConstructorThingy
{
    class Program
    {
        static void Main()
        {
            // does not call ctor
            var myClass = (MyClass)FormatterServices.GetUninitializedObject(typeof(MyClass));

            Console.WriteLine(myClass.One); // writes "0", constructor not called
            Console.WriteLine(myClass.Two); // writes "0", field initializer not called
        }
    }

    public class MyClass
    {
        public MyClass()
        {
            Console.WriteLine("MyClass ctor called.");
            One = 1;
        }

        public int One { get; private set; }
        public readonly int Two = 2;
    }
}

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