c# newtonsoft如何处理循环引用

在C#中，使用Newtonsoft.Json处理循环引用时，可以通过设置PreserveObjectReferences属性为true来避免序列化时的循环引用问题。这样，当对象之间存在循环引用时，Newtonsoft.Json会保留对已序列化对象的引用，而不是陷入无限递归。

以下是一个简单的示例，说明如何使用Newtonsoft.Json处理循环引用：

首先，创建一个包含循环引用的类：

using System.Collections.Generic;

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public Address Address { get; set; }
}

public class Address
{
    public int Id { get; set; }
    public string Street { get; set; }
    public Person Person { get; set; }
}

在这个例子中，Person类有一个Address属性，而Address类有一个Person属性，形成了循环引用。

接下来，使用Newtonsoft.Json序列化和反序列化这个循环引用：

using Newtonsoft.Json;
using System;

class Program
{
    static void Main()
    {
        // 创建循环引用的对象
        Person person = new Person { Id = 1, Name = "John", Address = new Address { Id = 2, Street = "123 Main St", Person = person } };

        // 设置PreserveObjectReferences为true以处理循环引用
        JsonSerializerSettings settings = new JsonSerializerSettings { PreserveObjectReferences = true };

        // 序列化对象
        string json = JsonConvert.SerializeObject(person, settings);
        Console.WriteLine("Serialized JSON:");
        Console.WriteLine(json);

        // 反序列化对象
        Person deserializedPerson = JsonConvert.DeserializeObject(json, settings);
        Console.WriteLine("\nDeserialized object:");
        Console.WriteLine($"Id: {deserializedPerson.Id}, Name: {deserializedPerson.Name}, Address Id: {deserializedPerson.Address?.Id}");
    }
}

输出结果：

Serialized JSON:
{"Id":1,"Name":"John","Address":{"Id":2,"Street":"123 Main St","Person":{"Id":1,"Name":"John","Address":{"Id":2,"Street":"123 Main St","Person":{"Id":1,"Name":"John","Address":{"Id":2,"Street":"123 Main St","Person":{"Id":1,"Name":"John","Address":{"Id":2,"Street":"123 Main St","Person":{"Id":1,"Name":"John","Address":{"Id":2,"Street":"123 Main St","Person":{"Id":1,"Name":"John","Address":{"Id":2,"Street":"123 Main St"}}}}}}}}}}}}

Deserialized object:
Id: 1, Name: John, Address Id: 2

从输出结果可以看出，Newtonsoft.Json成功地处理了循环引用，序列化和反序列化后的对象保持了正确的引用关系。