c# - .NET 反序列化与 OnDeserializing 和 OnDeserialized

Question

我使用一个可序列化的简单类。它有一个用于反序列化的构造函数:

protected MyClass(SerializationInfo info, StreamingContext context)

和一个用于序列化的 GetObjectData 方法。它工作正常。

现在我添加了两个方法来监控反序列化:

        [OnDeserializing()]
    internal void OnDeserializingMethod(StreamingContext context)
    {
        System.Diagnostics.Trace.WriteLine("OnDeserializingMethod: " + this.GetType().ToString());
    }

    [OnDeserialized()]
    internal void OnDeserializedMethod(StreamingContext context)
    {
        System.Diagnostics.Trace.WriteLine("OnDeserializedMethod: " + this.GetType().ToString());
    }

并且想知道这些方法的调用顺序。现在这两个方法都在调用构造函数之前被调用。这怎么可能，为什么在调用(反序列化-)构造函数之后不调用“OnDeserialized”方法？在执行任何构造函数之前如何调用(非静态)方法？ (我正在使用 BinaryFormatter)

Answer 1

Now both methods get called before the constructor gets called

不，顺序是:

• OnDeserializingMethod
• .ctor
• OnDeserializedMethod

And how can a (non-static) method be called before any constructor has been executed?

因为它欺骗和说谎；它不使用构造函数创建对象；不完全是。它使用 FormatterServices.GetUninitializedObject 分配 Vanilla 空白空间。然后，如果有自定义反序列化构造函数，它会在该对象的顶部调用构造函数。可恶的。像这样，基本上:

var obj = FormatterServices.GetUninitializedObject(typeof(MyClass));
var ctor = obj.GetType().GetConstructor(
    BindingFlags.Instance | BindingFlags.Public| BindingFlags.NonPublic,
    null,
    new[] { typeof(SerializationInfo), typeof(StreamingContext) },
    null);
ctor.Invoke(obj, new object[2]);

IMO 他们可能应该将此作为 ISerializable 接口(interface)上的第二个方法，但出于某种原因:他们没有这样做。真的很遗憾:这会让它更诚实，并且避免人们需要记住实现自定义构造函数。

示例输出:

.ctor: MyClass
> serializing
OnSerializingMethod: MyClass
GetObjectData: MyClass
OnSerializedMethod: MyClass
< serializing
> deserializing
OnDeserializingMethod: MyClass
.ctor: MyClass
OnDeserializedMethod: MyClass
< deserializing

示例代码:

using System;
using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
[Serializable]
class MyClass : ISerializable
{
    public MyClass() { Trace(); }
    protected MyClass(SerializationInfo info, StreamingContext context) { Trace(); }
    public void GetObjectData(SerializationInfo info, StreamingContext context) { Trace(); }
    void Trace([CallerMemberName] string caller = null)
    {
        System.Console.WriteLine("{0}: {1}", caller, GetType().Name);
    }
    [OnDeserializing()]
    internal void OnDeserializingMethod(StreamingContext context) { Trace(); }

    [OnDeserialized()]
    internal void OnDeserializedMethod(StreamingContext context) { Trace(); }

    [OnSerializing()]
    internal void OnSerializingMethod(StreamingContext context) { Trace(); }

    [OnSerialized()]
    internal void OnSerializedMethod(StreamingContext context) { Trace(); }

    static void Main()
    {
        using (var ms = new MemoryStream())
        {
            var orig = new MyClass();
            var ser = new BinaryFormatter();
            System.Console.WriteLine("> serializing");
            ser.Serialize(ms, orig);
            System.Console.WriteLine("< serializing");
            ms.Position = 0;
            System.Console.WriteLine("> deserializing");
            ser.Deserialize(ms);
            System.Console.WriteLine("< deserializing");
        }
    }
}