Help Deserialize JSON string into list of objects?

[BitFlipper88]

Hi,

I am a novice vb.net programmer. I am trying to deserialize a JSON string into a LIST of objects.

Here is the json...

{
   "categories":[
      {
         "id":"16310161",
         "name":"Industrial & Scientific",
         "has_children":true,
         "is_root":true,
         "path":"Industrial & Scientific",
         "link":"https://www.amazon.com/s?node=16310161",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"301668",
         "name":"CDs & Vinyl",
         "has_children":true,
         "is_root":true,
         "path":"CDs & Vinyl",
         "link":"https://www.amazon.com/s?node=301668",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"10677470011",
         "name":"Vehicles",
         "has_children":false,
         "is_root":true,
         "path":"Vehicles",
         "link":"https://www.amazon.com/s?node=10677470011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"4991426011",
         "name":"Collectibles & Fine Arts",
         "has_children":true,
         "is_root":true,
         "path":"Collectibles & Fine Arts",
         "link":"https://www.amazon.com/s?node=4991426011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"165795011",
         "name":"Toys & Games",
         "has_children":true,
         "is_root":true,
         "path":"Toys & Games",
         "link":"https://www.amazon.com/s?node=165795011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2335753011",
         "name":"Cell Phones & Accessories",
         "has_children":false,
         "is_root":true,
         "path":"Cell Phones & Accessories",
         "link":"https://www.amazon.com/s?node=2335753011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"11846801",
         "name":"Video Games",
         "has_children":true,
         "is_root":true,
         "path":"Video Games",
         "link":"https://www.amazon.com/s?node=11846801",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"11965861",
         "name":"Musical Instruments",
         "has_children":true,
         "is_root":true,
         "path":"Musical Instruments",
         "link":"https://www.amazon.com/s?node=11965861",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"3375301",
         "name":"Sports & Outdoors",
         "has_children":true,
         "is_root":true,
         "path":"Sports & Outdoors",
         "link":"https://www.amazon.com/s?node=3375301",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"468240",
         "name":"Tools & Home Improvement",
         "has_children":true,
         "is_root":true,
         "path":"Tools & Home Improvement",
         "link":"https://www.amazon.com/s?node=468240",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2619526011",
         "name":"Appliances",
         "has_children":true,
         "is_root":true,
         "path":"Appliances",
         "link":"https://www.amazon.com/s?node=2619526011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"15690151",
         "name":"Automotive",
         "has_children":true,
         "is_root":true,
         "path":"Automotive",
         "link":"https://www.amazon.com/s?node=15690151",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"3760931",
         "name":"Health & Personal Care",
         "has_children":true,
         "is_root":true,
         "path":"Health & Personal Care",
         "link":"https://www.amazon.com/s?node=3760931",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"1084128",
         "name":"Office Products",
         "has_children":true,
         "is_root":true,
         "path":"Office Products",
         "link":"https://www.amazon.com/s?node=1084128",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2864120011",
         "name":"Gift Cards",
         "has_children":true,
         "is_root":true,
         "path":"Gift Cards",
         "link":"https://www.amazon.com/s?node=2864120011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"409488",
         "name":"Software",
         "has_children":true,
         "is_root":true,
         "path":"Software",
         "link":"https://www.amazon.com/s?node=409488",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"1063498",
         "name":"Home & Kitchen",
         "has_children":true,
         "is_root":true,
         "path":"Home & Kitchen",
         "link":"https://www.amazon.com/s?node=1063498",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2617942011",
         "name":"Arts, Crafts & Sewing",
         "has_children":true,
         "is_root":true,
         "path":"Arts, Crafts & Sewing",
         "link":"https://www.amazon.com/s?node=2617942011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"3238155011",
         "name":"Patio, Lawn & Garden",
         "has_children":true,
         "is_root":true,
         "path":"Patio, Lawn & Garden",
         "link":"https://www.amazon.com/s?node=3238155011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2858778011",
         "name":"Amazon Instant Video",
         "has_children":true,
         "is_root":true,
         "path":"Amazon Instant Video",
         "link":"https://www.amazon.com/s?node=2858778011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"493964",
         "name":"Electronics",
         "has_children":true,
         "is_root":true,
         "path":"Electronics",
         "link":"https://www.amazon.com/s?node=493964",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"624868011",
         "name":"Digital Music",
         "has_children":true,
         "is_root":true,
         "path":"Digital Music",
         "link":"https://www.amazon.com/s?node=624868011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"11260433011",
         "name":"Handmade",
         "has_children":true,
         "is_root":true,
         "path":"Handmade",
         "link":"https://www.amazon.com/s?node=11260433011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"165797011",
         "name":"Baby",
         "has_children":true,
         "is_root":true,
         "path":"Baby",
         "link":"https://www.amazon.com/s?node=165797011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"599872",
         "name":"Magazine Subscriptions",
         "has_children":true,
         "is_root":true,
         "path":"Magazine Subscriptions",
         "link":"https://www.amazon.com/s?node=599872",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2625374011",
         "name":"Movies & TV",
         "has_children":true,
         "is_root":true,
         "path":"Movies & TV",
         "link":"https://www.amazon.com/s?node=2625374011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"16310211",
         "name":"Grocery & Gourmet Food",
         "has_children":true,
         "is_root":true,
         "path":"Grocery & Gourmet Food",
         "link":"https://www.amazon.com/s?node=16310211",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"1000",
         "name":"Books",
         "has_children":true,
         "is_root":true,
         "path":"Books",
         "link":"https://www.amazon.com/s?node=1000",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"133141011",
         "name":"Kindle Store",
         "has_children":true,
         "is_root":true,
         "path":"Kindle Store",
         "link":"https://www.amazon.com/s?node=133141011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"11055981",
         "name":"Beauty",
         "has_children":true,
         "is_root":true,
         "path":"Beauty",
         "link":"https://www.amazon.com/s?node=11055981",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"7141124011",
         "name":"Clothing, Shoes & Jewelry",
         "has_children":true,
         "is_root":true,
         "path":"Clothing, Shoes & Jewelry",
         "link":"https://www.amazon.com/s?node=7141124011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2350150011",
         "name":"Apps & Games",
         "has_children":true,
         "is_root":true,
         "path":"Apps & Games",
         "link":"https://www.amazon.com/s?node=2350150011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"2619534011",
         "name":"Pet Supplies",
         "has_children":true,
         "is_root":true,
         "path":"Pet Supplies",
         "link":"https://www.amazon.com/s?node=2619534011",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"audible",
         "name":"Audible",
         "has_children":false,
         "is_root":true,
         "path":"Audible",
         "link":"https://www.amazon.com/s?node=audible",
         "type":"standard",
         "domain":"amazon.com"
      },
      {
         "id":"amazonfresh",
         "name":"Amazon Fresh",
         "has_children":false,
         "is_root":true,
         "path":"Amazon Fresh",
         "link":"https://www.amazon.com/s?node=amazonfresh",
         "type":"standard",
         "domain":"amazon.com"
      }
   ]
}

And I am using newtonsoft to deserialize. I am confused on how this even works. All I would like is a simple way to organize this info and read fields from a list. For instance, I need all the IDs, or names... I don't necessarily need them to be placed into an object, although thats probably the best way.


So here is my object to deserialize into....

Public Class CategoryContainer
        Public ID As String
        Public Type As String
        Public Name As String
        Public HasChildren As Boolean
        Public IsRoot As Boolean
        Public Path As String
        Public Link As String
    End Class

And here is how I attempt to deserialize....

Dim cat = JsonConvert.DeserializeObject(Of List(Of CategoryContainer))(str)  'str = json string

And the failure is...

Newtonsoft.Json.JsonSerializationException: 'Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[Project1.Module3+CategoryContainer]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.

[.paul.]

Try this...

Public Class Rootobject
    Public Property categories As List(Of Category)
End Class

Public Class Category
    Public Property id As String
    Public Property name As String
    Public Property has_children As Boolean
    Public Property is_root As Boolean
    Public Property path As String
    Public Property link As String
    Public Property type As String
    Public Property domain As String
End Class

Imports Newtonsoft.Json
Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim str As String = IO.File.ReadAllText("json.txt")
        Dim cat = JsonConvert.DeserializeObject(Of Rootobject)(str)
        Stop
    End Sub
End Class

[BitFlipper88]

Paul,

Thanks for your help.

Unfortunately this did not solve the problem.

Here is code snippets...

   Public Class CategoryContainer
        Public id As String
        Public type As String
        Public name As String
        Public has_children As Boolean
        Public is_root As Boolean
        Public path As String
        Public link As String
        Public domain As String
    End Class

    Public Class CategoryContainerList
        Public Property ContainerList As List(Of CategoryContainer)
    End Class

Dim cat = JsonConvert.DeserializeObject(Of CategoryContainerList)(str)
Debug.Print(cat.ContainerList.ToString)

And the deserialization apparently returns nothing?.....

System.NullReferenceException: 'Object reference not set to an instance of an object.'

Project1.Module3.CategoryContainerList.ContainerList.get returned Nothing.

[BitFlipper88]

Update:

I changed the root (list) classes' property 'ContainerList' to match the JSON file 'categories' and the solution worked!

Didn't think that would matter. Thanks so much for your help!!

    Public Class CategoryContainer
        Public Property id As String
        Public Property name As String
        Public Property has_children As Boolean
        Public Property is_root As Boolean
        Public Property link As String
        Public Property path As String
        Public Property type As String
        Public Property domain As String
    End Class

    Public Class CategoryContainerList
        Public Property categories As List(Of CategoryContainer) 'this property name must match json array name 'categories' !
    End Class

[.paul.]

Try this...

Public Class CategoryContainerList
    @JsonProperty("categories")
    Public Property ContainerList As List(Of CategoryContainer) 
End Class

[.paul.]

Here's the correct syntax for VB...

Imports Newtonsoft.Json

Public Class CategoryContainerList
    <JsonProperty("categories")>
    Public Property ContainerList As List(Of CategoryContainer)
End Class

Public Class CategoryContainer
    Public Property id As String
    Public Property name As String
    Public Property has_children As Boolean
    Public Property is_root As Boolean
    Public Property path As String
    Public Property link As String
    Public Property type As String
    Public Property domain As String
End Class

Public Class Form1
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim str As String = IO.File.ReadAllText("json.txt")
        Dim cat = JsonConvert.DeserializeObject(Of CategoryContainerList)(str)
        Stop
    End Sub
End Class

[BitFlipper88]

Paul,

I tried adding the <json property> tag above the CategoryContainer class properties originally.

Thanks for adding that in there. Also, what is that line of code called, the json property tags?

[techgnome]

They're called annotations.

That one is specifically called a json property annotation.


-tg

[.paul.]

Paul,

I tried adding the <json property> tag above the CategoryContainer class properties originally.

Thanks for adding that in there. Also, what is that line of code called, the json property tags?

As tg told you…
The class structure layout works with just one json property annotation because all the other properties have the same names as the properties in the json file. The class names aren’t important.