VB.NET如何反序列化嵌套数组格式的JSON字符串？

给定JSON字符串：

[[5389809,"*Bella*@",0,"",0,"","y",1],[9888723,"bizarre",0,"",0,"","y",1],[9889781,"violate",0,"",0,"","y",1],[1510819,"xeno",1,"",0,"","y",1]]

我尝试使用以下自定义对象类反序列化：

Public Class MyFriendsList
    Public Property Array() As List(Of CategoryContainer)
End Class

Public Class CategoryContainer
    Public Property id As Integer
    Public Property user As String
End Class

但运行报错：

Newtonsoft.Json.JsonSerializationException: "Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'xMessenger.MyFriendsList' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly. To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection

错误根源 #

你的JSON是数组的数组（外层为数组，每个子元素也是包含8个值的有序数组），但你试图将其反序列化为带Array属性的MyFriendsList对象——这种结构要求JSON顶层是{"Array": [...]}格式的对象，和当前JSON的数组结构完全不匹配，因此序列化器抛出类型不匹配的错误。

解决思路 #

方法1：强类型反序列化（推荐）

修改CategoryContainer类，用JsonProperty特性指定属性对应JSON子数组的索引（因为JSON子数组是有序的，没有键名），然后直接反序列化为List(Of CategoryContainer)：

Imports Newtonsoft.Json

Public Class CategoryContainer
    <JsonProperty(Order := 0)> ' 对应子数组第1个元素（索引0）
    Public Property id As Integer
    <JsonProperty(Order := 1)> ' 对应子数组第2个元素（索引1）
    Public Property user As String
    ' 若需要后续字段，可按顺序添加对应属性
    <JsonProperty(Order := 2)>
    Public Property Status1 As Integer
    <JsonProperty(Order := 3)>
    Public Property ExtraStr1 As String
    <JsonProperty(Order := 4)>
    Public Property Status2 As Integer
    <JsonProperty(Order := 5)>
    Public Property ExtraStr2 As String
    <JsonProperty(Order := 6)>
    Public Property Flag As String
    <JsonProperty(Order := 7)>
    Public Property Status3 As Integer
End Class

反序列化代码：

Dim jsonContent = "[[5389809,""*Bella*@"",0,"""",0,"""",""y"",1],[9888723,""bizarre"",0,"""",0,"""",""y"",1],[9889781,""violate"",0,"""",0,"""",""y"",1],[1510819,""xeno"",1,"""",0,"""",""y"",1]]"
Dim friendsList = JsonConvert.DeserializeObject(Of List(Of CategoryContainer))(jsonContent)

方法2：手动解析无类型数组

如果不需要完整强类型，可先反序列化为数组的数组，再手动提取所需字段：

Dim rawArray = JsonConvert.DeserializeObject(Of List(Of Object()))(jsonContent)
Dim friendsList = New List(Of CategoryContainer)()

For Each item In rawArray
    friendsList.Add(New CategoryContainer With {
        .id = CInt(item(0)),
        .user = CStr(item(1))
    })
Next

方法3：保留MyFriendsList类的兼容方案

若必须使用MyFriendsList作为最终类型，可先反序列化为列表，再手动包装：

Dim innerList = JsonConvert.DeserializeObject(Of List(Of CategoryContainer))(jsonContent)
Dim myFriendsList = New MyFriendsList With {.Array = innerList}

内容的提问来源于stack exchange，提问作者xeno