BinaryFormatter 怎么可以序列化一个 Action<>但 Json.net 不能

同样的(ish)失败.

Same(ish) failure.

尝试 #3然后我发现 http://mikehadlow.blogspot.com/2011/04/serializing-continuations.html

Try # 3 Then I found http://mikehadlow.blogspot.com/2011/04/serializing-continuations.html

这使用 BinaryFormatter.我将其放入(base64 将二进制编码为字符串).第一次完美运行.

This uses BinaryFormatter. I dropped this in (base64 encoding the binary to a string). Worked perfectly first time.

尝试#4

然后我找到了

https://github.com/DevrexLabs/Modules.JsonNetFormatter

这是 json.net 的 IFormatter 模块.连线，同样的失败 - 无法反序列化.

Which is an IFormatter module for json.net. Wired that in, same failure - cannot deserialize.

那么为什么 BinaryFormatter 可以做到，而 Json.net 却不能呢?

So how come BinaryFormatter can do it but Json.net cannot?

一般的回答是 - 这是最愚蠢的事情".让我展示一下我想要做什么

The general reply is - "thats the most stupid thing to want to do". Let me show what I am trying to do

MyJobSystem.AddJob(ctx=>
{
   // code to do
   // ......
}, DateTime.UtcNow + TimeSpan.FromDays(2));

即 - 在 2 天内执行此 lambda.

Ie - execute this lambda in 2 days time.

这对我来说很好.使用 BinaryFormatter.我很好奇为什么一个序列化基础设施可以做到，而另一个不能.他们似乎对什么可以处理和不可以处理有相同的规则

This works fine for me. Using BinaryFormatter. I was curious about why one serializing infrastructure could do it but the other could not. They both seem to have the same rules about what can and cannot be processed

推荐答案

BinaryFormatter (有时)能够往返 Action< 的原因T> 是这样的代表被标记为 [Serializable] 并实现 ISerializable.

The reason that BinaryFormatter is (sometimes) able to round-trip an Action<T> is that such delegates are marked as [Serializable] and implement ISerializable.

但是，仅仅因为委托本身被标记为可序列化并不意味着它的成员可以成功序列化.在测试中，我能够序列化以下委托:

However, just because the delegate itself is marked as serializable doesn't mean that its members can be serialized successfully. In testing, I was able to serialize the following delegate:

Action<int> a1 = (a) => Console.WriteLine(a);

但尝试序列化以下内容会引发 SerializationException:

But attempting to serialize the following threw a SerializationException:

int i = 0;
Action<int> a2 = (a) => i = i + a;

捕获的变量 i 显然被放置在一个不可序列化的编译器生成的类中，从而阻止了委托的二进制序列化成功.

The captured variable i apparently is placed in a non-serializable compiler-generated class thereby preventing binary serialization of the delegate from succeeding.

另一方面，Json.NET 无法往返 Action<T> 尽管 支持 ISerializable，因为它不支持通过 SerializationInfo.SetType(Type).我们可以通过以下代码确认 Action<T> 正在使用这种机制:

On the other hand, Json.NET is unable to round-trip an Action<T> despite supporting ISerializable because it does not provide support for serialization proxies configured via SerializationInfo.SetType(Type). We can confirm that Action<T> is using this mechanism with the following code:

var iSerializable = a1 as ISerializable;
if (iSerializable != null)
{
    var info = new SerializationInfo(a1.GetType(), new FormatterConverter());
    var initialFullTypeName = info.FullTypeName;
    iSerializable.GetObjectData(info, new StreamingContext(StreamingContextStates.All));
    Console.WriteLine("Initial FullTypeName = "{0}", final FullTypeName = "{1}".", initialFullTypeName, info.FullTypeName);
    var enumerator = info.GetEnumerator();
    while (enumerator.MoveNext())
    {
        Console.WriteLine("   Name = {0}, objectType = {1}, value = {2}.", enumerator.Name, enumerator.ObjectType, enumerator.Value);
    }
}

运行时输出:

Initial FullTypeName = "System.Action`1[[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]", final FullTypeName = "System.DelegateSerializationHolder".
   Name = Delegate, objectType = System.DelegateSerializationHolder+DelegateEntry, value = System.DelegateSerializationHolder+DelegateEntry.
   Name = method0, objectType = System.Reflection.RuntimeMethodInfo, value = Void <Test>b__0(Int32).

请注意，FullTypeName 已更改为 System.DelegateSerializationHolder?那是代理，Json.NET 不支持.

Notice that FullTypeName has changed to System.DelegateSerializationHolder? That's the proxy, and it's not supported by Json.NET.

这就引出了一个问题，当委托被序列化时，到底写出什么?为了确定这一点，我们可以配置 Json.NET 来序列化 Action，类似于BinaryFormatter 如何设置

This begs the question, just what is written out when a delegate is serialized? To determine this we can configure Json.NET to serialize Action<T> similarly to how BinaryFormatter would by setting

• DefaultContractResolver.IgnoreSerializableAttribute = false
• DefaultContractResolver.IgnoreSerializableInterface = false
• JsonSerializerSettings.TypeNameHandling = TypeNameHandling.All

如果我使用这些设置序列化 a1:

If I serialize a1 using these settings:

var settings = new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.All,
    ContractResolver = new DefaultContractResolver
    {
        IgnoreSerializableInterface = false,
        IgnoreSerializableAttribute = false,
    },
    Formatting = Formatting.Indented,
};
var json = JsonConvert.SerializeObject(a1, settings);
Console.WriteLine(json);

然后生成以下JSON:

Then the following JSON is generated:

{
  "$type": "System.Action`1[[System.Int32, mscorlib]], mscorlib",
  "Delegate": {
    "$type": "System.DelegateSerializationHolder+DelegateEntry, mscorlib",
    "type": "System.Action`1[[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]",
    "assembly": "mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089",
    "target": null,
    "targetTypeAssembly": "Tile, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null",
    "targetTypeName": "Question49138328.TestClass",
    "methodName": "<Test>b__0",
    "delegateEntry": null
  },
  "method0": {
    "$type": "System.Reflection.RuntimeMethodInfo, mscorlib",
    "Name": "<Test>b__0",
    "AssemblyName": "Tile, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null",
    "ClassName": "Question49138328.TestClass",
    "Signature": "Void <Test>b__0(Int32)",
    "MemberType": 8,
    "GenericArguments": null
  }
}