VB.NET中如何反序列化并遍历JSON数组及嵌套数据

问题背景 #

原始JSON数据 #

{
    "TNS-API-KEY": "ABCD134EFG456HIJK678LMNOP",
    "docno": "35829",
    "idtns": "abc12345",
    "action": "6",
    "reason": "test -test",
    "userid": "450",
    "data": [
        {
            "pr": "0222/ATL/MIX/01/2021",
            "idpr": "13562",
            "cost": {
                "26217": {
                    "50662": {
                        "costingid": "26217",
                        "costid": "50662",
                        "gpro": "SSM",
                        "dbp": "18000",
                        "ppn": "0"
                    },
                    "50664": {
                        "costingid": "26217",
                        "costid": "50664",
                        "gpro": "SBL",
                        "dbp": "40500",
                        "ppn": "0"
                    }
                }
            }
        },
        {
            "pr": "123/AB/MIX/07/2022",
            "idpr": "17461",
            "cost": {
                "34876": {
                    "66194": {
                        "costingid": "34876",
                        "costid": "66194",
                        "gpro": "CCL",
                        "dbp": "1000000",
                        "ppn": "110000.00"
                    }
                },
                "34877": {
                    "66195": {
                        "costingid": "34877",
                        "costid": "66195",
                        "gpro": "TB",
                        "dbp": "2000000",
                        "ppn": "220000.00"
                    }
                }
            }
        }
    ]
}

需求说明 #

需要从每个PR条目里提取以下字段：

• costingid
• costid
• gpro
• dbp
• ppn

现有代码 #

已经能获取到data数组及PR编号，代码如下：

Dim jsonData As JObject = JObject.Parse(json)
Dim data As String = jsonData.SelectToken("data").ToString()
Dim jsonArray As JArray = JArray.Parse(jsonData.SelectToken("data").ToString)

For Each item As JObject In jsonArray
    Dim pr As String = (item.SelectToken("pr").ToString)
Next

疑问 #

如何获取嵌套在内层的数据？由于cost下的键是动态的（比如26217、34876这类无固定名称的键），不知道怎么进行内层循环处理。

解决方案 #

针对动态键的嵌套结构，可以通过遍历JObject的Properties来处理每一层动态节点，完整代码如下：

Imports Newtonsoft.Json.Linq

' 解析JSON
Dim jsonData As JObject = JObject.Parse(json)
Dim jsonArray As JArray = jsonData.SelectToken("data")

' 遍历每个PR条目
For Each prItem As JObject In jsonArray
    Dim prNumber As String = prItem.SelectToken("pr").ToString()
    Console.WriteLine($"PR编号: {prNumber}")
    
    ' 获取cost节点
    Dim costObj As JObject = prItem.SelectToken("cost")
    If costObj IsNot Nothing Then
        ' 遍历第一层动态键（对应costingid的键）
        For Each costingProp As JProperty In costObj.Properties()
            ' 获取costing节点下的所有cost子节点
            Dim costSubObj As JObject = costingProp.Value
            ' 遍历第二层动态键（对应costid的键）
            For Each costProp As JProperty In costSubObj.Properties()
                ' 提取目标字段
                Dim costDetail As JObject = costProp.Value
                Dim costingid As String = costDetail.SelectToken("costingid").ToString()
                Dim costid As String = costDetail.SelectToken("costid").ToString()
                Dim gpro As String = costDetail.SelectToken("gpro").ToString()
                Dim dbp As String = costDetail.SelectToken("dbp").ToString()
                Dim ppn As String = costDetail.SelectToken("ppn").ToString()
                
                ' 输出或处理提取到的数据
                Console.WriteLine($"  costingid: {costingid}, costid: {costid}, gpro: {gpro}, dbp: {dbp}, ppn: {ppn}")
            Next
        Next
    End If
Next

代码说明 #

1. 简化JSON解析：直接从jsonData获取data数组，无需额外转字符串再解析，减少冗余操作。
2. 处理动态键层级：
   • 第一层遍历cost对象的所有属性，每个属性的键对应costingid，值是包含多个costid的节点。
   • 第二层遍历每个costing节点下的属性，每个属性的键对应costid，值就是包含目标字段的对象。
3. 字段提取：从最内层的JObject直接通过SelectToken提取所需字段，无需依赖动态键名称。

内容的提问来源于stack exchange，提问作者Lydia