使用XML序列化时的循环引用？

Question

尝试使用XMLSerialization序列化对象时,我收到以下异常.

A circular reference was detected while serializing an object of type MyObject}

我知道循环引用是因为ObjectA可以有一个childObjectObjectB而ObjectB parentObject是ObjectA,但是如果可能的话我想保留该引用.有没有办法让这个对象在XML序列化中序列化而不会在序列化过程中丢失任何数据？我对序列化并不熟悉,所以我希望我能设置一些属性.

Answer 1

根据序列化器类型,有几个选项.

如果您可以使用DataContractSerializer或BinaryFormatter,那么您可以使用OnSerializedAttribute并将子对象的Parent属性设置为:

[Serializable]
public class Child
{
    public string Foo { get; set; }

    public Parent Parent { get { return parent; } set { parent = value; } }

    // We don't want to serialize this property explicitly.
    // But we could set it during parent deserialization
    [NonSerialized]
    private Parent parent;
}

[Serializable]
public class Parent
{
    // BinaryFormatter or DataContractSerializer whould call this method
    // during deserialization
    [OnDeserialized()]
    internal void OnSerializedMethod(StreamingContext context)
    {
        // Setting this as parent property for Child object
        Child.Parent = this;
    }

    public string Boo { get; set; }

    public Child Child { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        Child c = new Child { Foo = "Foo" };
        Parent p = new Parent { Boo = "Boo", Child = c };

        using (var stream1 = new MemoryStream())
        {
            DataContractSerializer serializer = new DataContractSerializer(typeof (Parent));
            serializer.WriteObject(stream1, p);
            stream1.Position = 0;
            var p2 = (Parent)serializer.ReadObject(stream1);

            Console.WriteLine(object.ReferenceEquals(p, p2)); //return false
            Console.WriteLine(p2.Boo); //Prints "Boo"

            //Prints: Is Parent not null: True
            Console.WriteLine("Is Parent not null: {0}", p2.Child.Parent != null);
        }
    }

}

如果要使用XmlSerializer,则应实现IXmlSerializable,使用XmlIgnoreAttribute并在ReadXml方法中实现或多或少相同的逻辑.但在这种情况下,您还应手动实现所有Xml序列化逻辑:

[Serializable]
public class Child
{
    public Child()
    {
    }

    public string Foo { get; set; }

    [XmlIgnore]
    public Parent Parent { get; set; }
}

[Serializable]
public class Parent
{
    public Parent()
    {
    }

    #region IXmlSerializable Members

    public System.Xml.Schema.XmlSchema GetSchema()
    {
        throw new NotImplementedException();
    }

    public void ReadXml(System.Xml.XmlReader reader)
    {
        //Reading Parent content
        //Reading Child
        Child.Parent = this;
    }

    public void WriteXml(System.Xml.XmlWriter writer)
    {
        //Writing Parent and Child content
    }

    #endregion

    public string Boo { get; set; }

    public Child Child { get; set; }
}