How to deserialize nested JSON arrays with Json.Net? - json

Question

I want to deserialize the response of a HTTP-Request to Objects.
The Response looks like this:
[
"BeginOfEnumerable",
[
{
"StatusID": 12345,
"ItemID": 987654
}
],
"EndOfEnumerable"
]
I am using Newtonsoft.Json.
I tried to use Visual Studio's Edit > Paste special > Paste JSON as Classes to create the class model, but the result looks strange to me:
Public Class Rootobject
Public Property Property1() As Object
End Class
Also, this throws an Exception:
Dim myObject As Rootobject = JsonConvert.DeserializeObject(response.Content)
» Unexpected character encountered while parsing value: .Path ", line
0, position 0.
I want to get the StatusID and ItemID.
A JSON Validator I used says this JSON is valid.

Answer 1

The JSON structure is valid, per se, you may have some difficulty with the strings that don't follow the name:value pattern.
You could deserialize only the inner array of values, as a List(class), e.g.,
Imports System.Collections.Generic
Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq
Public Class EnumObject
Public Property StatusId As Long
Public Property ItemId As Long
End Class
'[...]
Dim jsonEnumsTokens = JArray.Parse(response.Content)
Dim enumsArray = jsonEnumsTokens.Children.Skip(1).First().ToObject(Of List(Of EnumObject))()
which returns the list of EnumObject that contain the values, if that's all you're interested in and you don't need to handle this JSON in any other way, or serialize it back in the same form.
If you want to get the JSON representation of the arrays only:
Dim justTheArraysJson = jsonEnumsTokens.Children.Skip(1).First().ToString()
In case you want to perform deserialization and serialization, maintaining the structure, you could use a custom JsonConverter that handles this case.
The EnumObjectsConverter creates an intermediate structure that contains both the single strings and the array of values, contained in the EnumObjectArray property.
This also allows to serialize back to the original structure, if needed.
Call it as:
Dim enumArray = EnumObjectsHandler.Deserialize(response.Content)
Dim serialized = EnumObjectsHandler.Serialize(enumArray)
The EnumObjectsHandler class that provides the static methods for the serialization:
Public Class EnumObjectsHandler
Private Shared settings As JsonSerializerSettings = New JsonSerializerSettings() With {
.Converters = {New EnumObjectsConverter()}
}
Public Shared Function Deserialize(json As String) As List(Of EnumObjectsRoot)
Return JsonConvert.DeserializeObject(Of List(Of EnumObjectsRoot))(json, settings)
End Function
Public Shared Function Serialize(data As List(Of EnumObjectsRoot)) As String
Return JsonConvert.SerializeObject(data, settings)
End Function
Public Class EnumObject
Public Property StatusId As Long
Public Property ItemId As Long
End Class
Public Structure EnumObjectsRoot
Public Property EnumObjectArray As List(Of EnumObject)
Public Property Operation As String
Public Shared Widening Operator CType(objectArray As List(Of EnumObject)) As EnumObjectsRoot
Return New EnumObjectsRoot With {.EnumObjectArray = objectArray}
End Operator
Public Shared Widening Operator CType(op As String) As EnumObjectsRoot
Return New EnumObjectsRoot With {.Operation = op}
End Operator
End Structure
Friend Class EnumObjectsConverter
Inherits JsonConverter
Public Overrides Function CanConvert(t As Type) As Boolean
Return t Is GetType(EnumObjectsRoot)
End Function
Public Overrides Function ReadJson(reader As JsonReader, t As Type, existingValue As Object, serializer As JsonSerializer) As Object
Select Case reader.TokenType
Case JsonToken.String
Dim stringValue = serializer.Deserialize(Of String)(reader)
Return New EnumObjectsRoot() With {
.Operation = stringValue
}
Case JsonToken.StartArray
Dim arrayValue = serializer.Deserialize(Of List(Of EnumObject))(reader)
Return New EnumObjectsRoot() With {
.EnumObjectArray = arrayValue
}
End Select
Throw New Exception("EnumObjectsRoot could not be deserialized")
End Function
Public Overrides Sub WriteJson(writer As JsonWriter, untypedValue As Object, serializer As JsonSerializer)
Dim value = CType(untypedValue, EnumObjectsRoot)
If value.Operation IsNot Nothing Then
serializer.Serialize(writer, value.Operation)
Return
End If
If value.EnumObjectArray IsNot Nothing Then
serializer.Serialize(writer, value.EnumObjectArray)
Return
End If
Throw New Exception("EnumObjectsRoot could not be serialized")
End Sub
End Class
End Class