.net XML 序列化 - 存储引用而不是对象副本 [英] .net XML Serialization - Storing Reference instead of Object Copy

问题描述

• 在 .Net/C# 应用程序中，我有相互引用的数据结构.
• 当我序列化它们时，.Net 使用单独的对象副本序列化所有引用.
• 在以下示例中，我尝试序列化为人"数组

• 一个人"可能会引用另一个人.

• In .Net/C# Application, I have data structures which have references to each other.
• When I serialize them, .Net Serializes all references with separate object copies.
• In Following Example, I am trying to serialize to Array of 'Person'

• A 'Person' may have reference to another person.

public class Person
{
    public string Name;
    public Person Friend;
}

Person p1 = new Person();
p1.Name = "John";

Person p2 = new Person();
p2.Name = "Mike";

p1.Friend = p2;

Person[] group = new Person[] { p1, p2 };
XmlSerializer ser = new XmlSerializer(typeof(Person[]));
using (TextWriter tw = new StreamWriter("test.xml"))
    ser.Serialize(tw,group );

//above code generates following xml

<ArrayOfPerson>
  <Person>
    <Name>John</Name>
    <Friend>
      <Name>Mike</Name>
    </Friend>
  </Person>
  <Person>
    <Name>Mike</Name>
  </Person>
</ArrayOfPerson>

在上面的代码中，同一个Mike"对象出现在两个地方，因为同一个对象有两个引用.

推荐答案

XmlSerializer.您可以通过 DataContractSerializer 使用PreserveObjectReferences 属性.你可以看看这个 post ，它解释了详情.

It is not possible with XmlSerializer. You could achieve this with DataContractSerializer using the PreserveObjectReferences property. You may take a look at this post which explains the details.

这是一个示例代码:

public class Person
{
    public string Name;
    public Person Friend;
}

class Program
{
    static void Main(string[] args)
    {
        Person p1 = new Person();
        p1.Name = "John";

        Person p2 = new Person();
        p2.Name = "Mike";
        p1.Friend = p2;
        Person[] group = new Person[] { p1, p2 };

        var serializer = new DataContractSerializer(group.GetType(), null, 
            0x7FFF /*maxItemsInObjectGraph*/, 
            false /*ignoreExtensionDataObject*/, 
            true /*preserveObjectReferences : this is where the magic happens */, 
            null /*dataContractSurrogate*/);
        serializer.WriteObject(Console.OpenStandardOutput(), group);
    }
}

这会生成以下 XML:

This produces the following XML:

<ArrayOfPerson z:Id="1" z:Size="2" xmlns="http://schemas.datacontract.org/2004/07/ToDelete" xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/">
    <Person z:Id="2">
        <Friend z:Id="3">
            <Friend i:nil="true"/>
            <Name z:Id="4">Mike</Name>
        </Friend>
        <Name z:Id="5">John</Name>
    </Person>
    <Person z:Ref="3" i:nil="true"/>
</ArrayOfPerson>

现在在构造函数中将 PreserveObjectReferences 设置为 false，您将得到:

Now set PreserveObjectReferences to false in the constructor and you will get this:

<ArrayOfPerson xmlns="http://schemas.datacontract.org/2004/07/ToDelete" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
    <Person>
        <Friend>
            <Friend i:nil="true"/>
            <Name>Mike</Name>
        </Friend>
        <Name>John</Name>
    </Person>
    <Person>
        <Friend i:nil="true"/>
        <Name>Mike</Name>
    </Person>
</ArrayOfPerson>

值得一提的是，这种方式生成的 XML 不能互操作，只能使用 DataContractSerializer 进行反序列化(与 BinaryFormatter).

It is worth mentioning that the XML produced this way is not interoperable and can only be deserialized with a DataContractSerializer (same remark as with the BinaryFormatter).

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