与SelectToken一起使用时，为什么AddAfterSelf返回"JProperty不能有多个值"? [英] Why does AddAfterSelf return 'JProperty cannot have multiple values' when used with SelectToken?

问题描述

我想使用字符串路径将新的JProperty添加到JSON对象. 我正在检索现有路径，然后在其附近添加一个新值. 似乎无论我如何选择令牌，还是无论我调用哪种Add方法(最相关的是AddAfterSelf)还是作为新值提供的东西，都会收到异常:

I want to add a new JProperty to a JSON object using a string path. I'm retrieving an existing path and then adding a new value proximal to it. It seems no matter how I select a token, or no matter what Add method I call (most relevant is AddAfterSelf) or what I supply as a new value, I receive the exception:

运行时异常(第9行):Newtonsoft.Json.Linq.JProperty不能具有多个值.

Run-time exception (line 9): Newtonsoft.Json.Linq.JProperty cannot have multiple values.

您会在这里看到失败: https://dotnetfiddle.net/mnvmOI

You can see this failing here: https://dotnetfiddle.net/mnvmOI

在这种情况下为什么不能添加JProperty?

Why can't I add a JProperty in this situation?

using System;
using Newtonsoft.Json.Linq;

public class Program
{
    public static void Main()
    {
        JObject test = JObject.Parse("{\"test\":123,\"deeper\":{\"another\":\"value\"}}");
        test.SelectToken("deeper.another").AddAfterSelf(new JProperty("new name","new value"));
    }
}

推荐答案

引发异常的原因是的JProperty所拥有的JValue.如果您这样做，可以看到以下内容:

The reason that the exception is thrown is that SelectToken() returns the property's JValue not the JProperty itself. Specifically, it returns a JValue owned by the JProperty with name "another". You can see this if you do:

Console.WriteLine("Result type: {0}; result parent type: {1}", result.GetType(), result.Parent.GetType());

会导致

Result type: Newtonsoft.Json.Linq.JValue; result parent type: Newtonsoft.Json.Linq.JProperty

如果进一步将对象类型从JToken层次结构的顶部打印到SelectToken()返回的值，您将看到JValue标记包含在JProperty标记内:

And if you further print the object types from the top of the JToken hierarchy to the value returned by SelectToken(), you will see the JValue tokens contained inside the JProperty tokens:

Depth: 0, Type: JObject
Depth: 1, Type: JProperty: deeper
Depth: 2, Type: JObject
Depth: 3, Type: JProperty: another
Depth: 4, Type: JValue: value

Json.NET文档还指示SelectToken()返回所选属性的值:

The Json.NET documentation also indicates that SelectToken() returns the selected property's value:

string name = (string)o.SelectToken("Manufacturers[0].Name");

Console.WriteLine(name);
// Acme Co

由于JProperty不能有多个值，因此当您尝试在层次结构中的值之后立即添加JProperty时，您尝试将其添加为其父级JProperty的子级，例外.

Since a JProperty cannot have more than one value, when you try to add a JProperty immediately after the value in the hierarchy, you are trying to add it as a child of its parent JProperty, which throws the exception.

相反，将其添加到父级的父级中:

Instead, add it to parent's parent:

test.SelectToken("deeper.another").Parent.AddAfterSelf(new JProperty("new name","new value"));

示例小提琴显示以上所有内容.

Sample fiddle showing all of the above.

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