VB.NET JSON反序列化报错：无法将JSON对象转为List`1类型求助

1. 反序列化目标类型不匹配：返回的JSON是一个顶层对象（FeatureCollection），而非直接的properties数组。你当前尝试将整个JSON对象反序列化为List(Of properties)，必然导致类型不匹配错误。
2. 实体模型结构错误：
   • AutoCompleteResponse中的features被定义为String，但JSON里features是对象数组，每个元素包含properties字段；
   • 模型中AutoCompleteResponse的Properties属性在JSON中不存在，完全对应错误；
   • 部分嵌套对象（如datasource、rank、timezone）被定义为String，无法正确映射JSON中的嵌套结构。

1. 修正实体模型 #

根据JSON结构，定义完整的对应类：

Public Class AutoCompleteResponse
    Public Property type As String
    Public Property features As List(Of Feature)
    Public Property query As Query
End Class

Public Class Feature
    Public Property type As String
    Public Property geometry As Geometry
    Public Property properties As Properties
End Class

Public Class Geometry
    Public Property type As String
    Public Property coordinates As List(Of Double)
End Class

Public Class Properties
    Public Property country_code As String
    Public Property housenumber As String
    Public Property street As String
    Public Property country As String
    Public Property county As String
    Public Property datasource As Datasource
    Public Property state As String
    Public Property district As String
    Public Property city As String
    Public Property lon As Double
    Public Property lat As Double
    Public Property postcode As String
    Public Property formatted As String
    Public Property address_line1 As String
    Public Property address_line2 As String
    Public Property timezone As Timezone
    Public Property plus_code As String
    Public Property plus_code_short As String
    Public Property result_type As String
    Public Property rank As Rank
    Public Property place_id As String
    Public Property county_code As String
End Class

Public Class Datasource
    Public Property sourcename As String
    Public Property attribution As String
    Public Property license As String
End Class

Public Class Timezone
    Public Property name As String
    Public Property offset_STD As String
    Public Property offset_STD_seconds As Integer
    Public Property offset_DST As String
    Public Property offset_DST_seconds As Integer
    Public Property abbreviation_STD As String
    Public Property abbreviation_DST As String
End Class

Public Class Rank
    Public Property popularity As Double
    Public Property confidence As Double
    Public Property match_type As String
End Class

Public Class Query
    Public Property text As String
    Public Property parsed As Parsed
End Class

Public Class Parsed
    Public Property housenumber As String
    Public Property street As String
    Public Property expected_type As String
End Class

2. 修正反序列化代码 #

先反序列化为AutoCompleteResponse对象，再从中提取properties列表：

' 反序列化顶层对象
Dim responseObj As AutoCompleteResponse = Newtonsoft.Json.JsonConvert.DeserializeObject(Of AutoCompleteResponse)(response)
' 提取所有properties
Dim test As List(Of Properties) = responseObj.features.Select(Function(f) f.properties).ToList()
e.Result = test

• 保持类名和属性名与JSON字段一致，避免潜在的大小写匹配问题；
• 数值类型修正：JSON中的lon、lat、popularity等是数值类型，模型中对应为Double而非String，确保数据类型匹配；
• 完整映射嵌套结构：所有JSON中的嵌套对象都需要对应定义类，否则会导致反序列化失败或数据丢失。

内容的提问来源于stack exchange，提问作者August Christopher Paras