使用反序列化数据访问字典中的数据答案

【问题标题】：Access Data in Dictionary with deserialized data使用反序列化数据访问字典中的数据
【发布时间】：2021-04-12 21:59:49
【问题描述】：

我的程序通过 Web API 访问数据并获取 JSON 格式的数据。响应例如：

{
   "response":{
      "stationId":"24026900",
      "prices":[
         {
            "name":"Aral Super E10",
            "price":"146,90",
            "currency":"EUR",
            "id":"001131",
            "sort":"21"
         },
         {
            "name":"Aral Super 95",
            "price":"152,90",
            "currency":"EUR",
            "id":"001040",
            "sort":"22"
         },
         {
            "name":"Aral Ultimate 102",
            "price":"172,90",
            "currency":"EUR",
            "id":"001255",
            "sort":"24"
         },
         {
            "name":"Aral Diesel",
            "price":"130,90",
            "currency":"EUR",
            "id":"004002",
            "sort":"30"
         },
         {
            "name":"Aral Ultimate Diesel",
            "price":"150,90",
            "currency":"EUR",
            "id":"004267",
            "sort":"31"
         },
         {
            "name":"Aral LKW Diesel",
            "price":"130,90",
            "currency":"EUR",
            "id":"004010",
            "sort":"32"
         }
      ],
      "lastUpdate":"202104122030",
      "disabled":"false",
      "openNow":"Wir haben f\u00fcr Sie ge\u00f6ffnet."
   }
}

我该怎么做？访问深度嵌套的数据，例如 "price":"172,90"。

我的结构是这样的：

Dim sJSON As String

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim PriceLastValue As String = funcGetPriceInfo("response") 'How to get access to deeper nested data here?
    '
    'Every key except "response" throws an exception
    '
    MsgBox(PriceLastValue.ToString)
End Sub

Private Function funcGetPriceInfo(ByVal sVal As String) As String
    Dim JSONSerializer As New System.Web.Script.Serialization.JavaScriptSerializer
    sJSON = ReadStreamFromWeb.ReadFileFromWeb_WebRequest("http://ap.aral.de/api/v2/getStationPricesById.php?stationId=24026900")
    Dim dictJSON As Dictionary(Of String, Object) = JSONSerializer.Deserialize(Of Dictionary(Of String, Object))(sJSON)
    Return dictJSON(sVal).ToString
End Function

【问题讨论】：

这是一个简单的结构。 Root 对象 response 包含 5 个属性。 prices 属性是 Price 对象的数组或列表。您可以通过索引访问数组中的每个对象。 -- 顺便说一句，您正在使用错误的编码读取 JSON 响应（请参阅 openNow 属性值，Wir haben f\u00fcr 应该是 Wir haben für）。您的 JSON 是 UTF-8 编码的。 -- 您可能应该将此 JSON 反序列化为类模型。 -- 需要使用JavaScriptSerializer吗？

标签： json vb.net javascriptserializer

【解决方案1】：

谢谢你，非常感谢你的帮助！现在添加了对 Newtonsoft 和类的引用：

Public Class Rootobject
    Public Property response As Response
End Class

Public Class Response
    Public Property stationId As String
    Public Property prices() As Price
    Public Property lastUpdate As String
    Public Property disabled As String
    Public Property openNow As String
End Class

Public Class Price
    Public Property name As String
    Public Property price As String
    Public Property currency As String
    Public Property id As String
    Public Property sort As String
End Class

并试图获取对象：

    sJSON = ReadStreamFromWeb.ReadFileFromWeb_WebRequest("http://ap.aral.de/api/v2/getStationPricesById.php?stationId=24026900")
    Dim obj As Rootobject = JsonConvert.DeserializeObject(Of Rootobject)(sJSON)

但这会引发..

Newtonsoft.Json.JsonSerializationException: "Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'myprog.Form1+Price' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.

【讨论】：

Public Property prices() As List(Of Price)。属性的这种格式：Public Property prices() As Price 具有误导性（因为在该语言的属性中使用了多余的 - 而非必需的括号），它定义了类型为 Price 的单个对象，而不是数组。