JSON Format Deserialize Error - json

Question

I am new to manipulating JSON format data retrieved through an Web API. I'm using Newtonsoft.Json.JsonConvert to deserialize and assign to datatable.
This is the JSON data I am trying to get into a datatable.
[{
"classDesc":"SIDEWALK,DRIVEWAY,CURB",
"classCode":"EH",
"legend":"017",
"isActive":"Y",
"atrSpaCityDistrictId":"00D17209F8F25F6D4A00011302",
"atrSpaCitieDistrict":{
"cityDistrict":"",
"isActive":"1",
"atrSpaClassLegends":null,
"id":"00D17209F8F25F6D4A00011302"
},
"id":"00D1748B8DA0AB0A7400011202"
}]
I have created the below classes
Public Class RootObject
Public Property classDesc As String
Public Property classCode As String
Public Property id As Integer
Public Property legend As Integer
Public Property isActive As String
Public Property atrSpaCityDistrictId As Integer
Public Property atrSpaCitieDistrict As List(Of Result) End Class
Public Class Result
Public Property cityDistrict As String
Public Property isActive As Integer
Public Property atrSpaClassLegends As List(Of Legend)
Public Property id As Integer
End Class
Public Class Legend
End Class
Below is my VB.Net code:
Dim table As DataTable Dim client As New HttpClient() client.BaseAddress = New Uri("http://localhost:5000/") client.DefaultRequestHeaders.Accept.Add(New MediaTypeWithQualityHeaderValue("application/json"))
Dim response As HttpResponseMessage = client.GetAsync("api/spaclasslegend").Result
If response.IsSuccessStatusCode Then
Dim json As String = response.Content.ReadAsStringAsync().Result table = JsonConvert.DeserializeObject(Of DataTable)(json)
End If
Getting below error
"Cannot deserialize the current JSON array (e.g. [1,2,3]) into type
'Alco.APTIS.Services.RootObject' because the type requires a JSON
object (e.g. {"name":"value"}) to deserialize correctly."
I have tried different ways to fix this using stackoverflow.com and finally posting here for help.

Answer 1

You have two unrelated issues.
Firstly, your root object doesn't match your JSON. If I copy your JSON into a code generator such as http://jsonutils.com/, I get the following, using a List(Of Legend) for the null atrSpaClassLegends property:
Public Class AtrSpaCitieDistrict
Public Property cityDistrict As String
Public Property isActive As String
Public Property atrSpaClassLegends As List(Of Legend)
Public Property id As String
End Class
Public Class RootObject
Public Property classDesc As String
Public Property classCode As String
Public Property legend As String
Public Property isActive As String
Public Property atrSpaCityDistrictId As String
Public Property atrSpaCitieDistrict As AtrSpaCitieDistrict
Public Property id As String
End Class
Public Class Legend
End Class
Having done this, it is now possible to deserialize your JSON into a List(Of RootObject):
Dim root = JsonConvert.DeserializeObject(Of List(Of RootObject))(jsonString)
Note you must deserialize as a List(Of RootObject) (or similar .Net collection such as an array) since your top level JSON container is a JSON array -- an ordered comma-separated sequence of values surrounded by [ and ]. This is explained in the Json.NET Serialization Guide. Sample fiddle.
Secondly, despite having created these types, in the code shown in your question you are not using them at all! Instead, you are deserializing to a DataTable. And unfortunately the atrSpaCitieDistrict property is a nested object:
{
"atrSpaCitieDistrict": {
"cityDistrict": "",
"isActive": "1",
"atrSpaClassLegends": null,
"id": "00D17209F8F25F6D4A00011302"
},
}
Json.NET does not support automatically deserializing column values that are complex objects into untyped data tables, and will throw an exception if one is encountered. Instead, you would need to deserialize into a typed data table. However, this may be a typo in your question; the exception error message indicates you are actually trying to deserialize into an object of type Alco.APTIS.Services.RootObject and not a DataTable.