在一个含有4层的Json数组中添加元素，并输出添加后的json

假设原始的 JSON 数组如下所示：

[
  {
    "id": 1,
    "name": "John",
    "age": 30,
    "children": [
      {
        "id": 100,
        "name": "Mary",
        "age": 5,
        "hobbies": [
          "reading",
          "painting"
        ]
      }
    ]
  },
  {
    "id": 2,
    "name": "Jane",
    "age": 35,
    "children": [
      {
        "id": 200,
        "name": "Bob",
        "age": 10,
        "hobbies": [
          "swimming",
          "dancing"
        ]
      },
      {
        "id": 201,
        "name": "Alice",
        "age": 8,
        "hobbies": [
          "singing",
          "playing instruments"
        ]
      }
    ]
  }
]

如果要在 `children` 数组中添加一个新的元素，可以使用以下代码：

// 解析 JSON 数组
JArray jsonArray = JArray.Parse(jsonString);

// 创建新的子元素
JObject newChild = new JObject();
newChild["id"] = 202;
newChild["name"] = "Tom";
newChild["age"] = 6;

// 添加新的子元素
jsonArray[1]["children"].Last.AddAfterSelf(newChild);

// 输出添加后的 JSON 数组
Console.WriteLine(jsonArray.ToString());

上述代码会在第二个对象中的 `children` 数组中添加一个新的元素，新元素的属性值为：

{
  "id": 202,
  "name": "Tom",
  "age": 6
}

输出的结果为：

[
  {
    "id": 1,
    "name": "John",
    "age": 30,
    "children": [
      {
        "id": 100,
        "name": "Mary",
        "age": 5,
        "hobbies": [
          "reading",
          "painting"
        ]
      }
    ]
  },
  {
    "id": 2,
    "name": "Jane",
    "age": 35,
    "children": [
      {
        "id": 200,
        "name": "Bob",
        "age": 10,
        "hobbies": [
          "swimming",
          "dancing"
        ]
      },
      {
        "id": 201,
        "name": "Alice",
        "age": 8,
        "hobbies": [
          "singing",
          "playing instruments"
        ]
      },
      {
        "id": 202,
        "name": "Tom",
        "age": 6
      }
    ]
  }
]

可以看到，新的元素已经成功添加到了 JSON 数组中。