Question

在我的两个类中工作时看起来像这样（最小）

using System;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
using System.IO;
using ProtoBuf;

namespace Sandbox
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            Family family = new Family();
            Child child1 = new Child(1);
            Child child2 = new Child(2);
            Parent parent = new Parent(new List<Child>() { child1, child2 });
            family.Add(parent);

            string file = "sandbox.txt";

            try { File.Delete(file); } catch { }

            using (var fs = File.OpenWrite(file)) { Serializer.Serialize(fs, family); }
            using (var fs = File.OpenRead(file)) { family = Serializer.Deserialize<Family>(fs); }

            System.Diagnostics.Debug.Assert(family != null, "1. Expect family not null, but not the case.");
        }
    }

    [ProtoContract()]
    public class Child
    {
        [ProtoMember(1, AsReference = true)]
        internal Parent Parent;

        private Child() { }

        public Child(int i) { }
    }

    [ProtoContract()]
    public class Parent
    {
        [ProtoMember(1)]
        protected List<Child> m_Children;

        /// <summary>
        /// ProtoBuf deserialization constructor (fails here)
        /// </summary>
        private Parent() { m_Children = new List<Child>(); }

        public Parent(List<Child> children)
        {
            m_Children = children;
            m_Children.ForEach(x => x.Parent = this);
        }
    }

    [ProtoContract()]
    public class Family
    {
        [ProtoMember(1)]
        protected List<Parent> m_Parents;

        public void Add(Parent parent)
        {
            m_Parents.Add(parent);
        }

        public Family()
        {
            m_Parents = new List<Parent>();
        }
    }
}

在反序列化期间，我遇到异常“没有为此对象定义无参数构造函数”。用于在

附近的ProtoBuf.BclHelper中创建Parent对象

case FieldObject:
// ...
value = ((options & NetObjectOptions.UseConstructor) == 0) ? BclHelpers.GetUninitializedObject(type) : Activator.CreateInstance(type);

然后当我将默认构造函数Parent（）更改为public时，异常就消失了。

在这种情况下，任何想法~~我可能忽略了什么~~是AsRerference的正确用法？

BOUNTY ：虽然Marc花时间来解决这个问题，但我需要一个明确的解决方案来在这种情况下使用protobuf-net，通过protobuf-net属性，方法或其他技巧来解决。否则我将不得不放弃使用protobuf-net。谢谢你的帮助。

Answer 1

我相信你可以这样做来解决这个问题：

[ProtoContract(SkipConstructor = true)]
public class Parent
{
    [ProtoMember(1)]
    protected List<Child> m_Children;

    private Parent() { Initialize(); }

    [ProtoBeforeDeserialization] // could also use OnDeserializing
    private void Initialize()
    {
        m_Children = new List<Child>();
    }

    public Parent(List<Child> children)
    {
        m_Children = children;
        m_Children.ForEach(x => x.Parent = this);
    }

}

Answer 2

反序列化Parent时，需要公共无参数构造函数。因此，失败的最小测试用例是：创建具有非空Child的{{1}}，对其进行序列化并反序列化结果。

ProtoBuf-net AsReference需要Activator.CreateInstance中的公共构造函数吗？

2 个答案: