I am making an application and I need to read a certain value from a json file.

The json file is formatted as follows...

{
  "files": [
    {
      "id": [
        6856,
        3667
      ],
      "uid": 15749645081288,
      "file_id": 6856,
      "name": "Name",
      "version": "001",
      "category_id": 4,
      "category_name": "OLD_VERSION",
      "is_primary": false,
      "size": 4,
      "file_name": "Name_001-1539-001-1633022640.zip",
      "uploaded_timestamp": 1633022640,
      "uploaded_time": "2021-09-30T17:24:00.000 00:00",
      "mod_version": "001",
      "external_virus_scan_url": "https://www.virustotal.com",
      "description": "Version 001 Public",
      "size_kb": 4,
      "size_in_bytes": 3961,
      "changelog_html": "Public",
      "content_preview_link": "URL"
    },
    {
      "id": [
        6872,
        3667
      ],
      "uid": 15749645081304,
      "file_id": 6872,
      "name": "Name_002",
      "version": "002",
      "category_id": 1,
      "category_name": "MAIN",
      "is_primary": true,
      "size": 4,
      "file_name": "Name_002-1539-002-1633106391.zip",
      "uploaded_timestamp": 1633106391,
      "uploaded_time": "2021-10-01T16:39:51.000 00:00",
      "mod_version": "002",
      "external_virus_scan_url": "https://www.virustotal.com/",
      "description": "Update 002 . See changelog.",
      "size_kb": 4,
      "size_in_bytes": 4150,
      "changelog_html": "Stuff",
      "content_preview_link": "URL"
    }
  ],
  "file_updates": [
    {
      "old_file_id": 6856,
      "new_file_id": 6872,
      "old_file_name": "Name_001-1539-001-1633022640.zip",
      "new_file_name": "Name_002-1539-002-1633106391.zip",
      "uploaded_timestamp": 1633106392,
      "uploaded_time": "2021-10-01T16:39:52.000 00:00"
    }
  ]
}

And I am in need of the "file_id" Value

The Code I have is as follows

    Dim json As String = ModLinkData(n)
    Dim read = Newtonsoft.Json.Linq.JObject.Parse(json)
    Dim FileID As String = read.Item("files").ToString

This will properly give me everything Under "files". I can not figure out how to ger the file_id value. When I change "files" to

CodePudding user response：

I like to use strong typing for this, so I would look into JSON Serialization

You can create a class in .NET by copying your json string to the clipboard, then

In Visual Studio put the cursor where you want the new classes
Edit >> Paste Special >> Paste JSON as Classes

And the result is this (I have changed some array types to Lists in Rootobject)

Public Class Rootobject
    Public Property files As List(Of File)
    Public Property file_updates As List(Of File_Updates)
End Class
Public Class File
    Public Property id As Integer()
    Public Property uid As Long
    Public Property file_id As Integer
    Public Property name As String
    Public Property version As String
    Public Property category_id As Integer
    Public Property category_name As String
    Public Property is_primary As Boolean
    Public Property size As Integer
    Public Property file_name As String
    Public Property uploaded_timestamp As Integer
    Public Property uploaded_time As Date
    Public Property mod_version As String
    Public Property external_virus_scan_url As String
    Public Property description As String
    Public Property size_kb As Integer
    Public Property size_in_bytes As Integer
    Public Property changelog_html As String
    Public Property content_preview_link As String
End Class
Public Class File_Updates
    Public Property old_file_id As Integer
    Public Property new_file_id As Integer
    Public Property old_file_name As String
    Public Property new_file_name As String
    Public Property uploaded_timestamp As Integer
    Public Property uploaded_time As Date
End Class

Since you are already referencing NewtonSoft.Json, we can use the deserialization method therein

Dim json = ModLinkData(n)

Dim rootobject = Newtonsoft.Json.JsonConvert.DeserializeObject(Of Rootobject)(json)

Dim fileIDs = rootobject.files.First().id ' this is an array
Dim fileID1 = fileIDs(0)
Dim fileID2 = fileIDs(1)

Console.WriteLine(fileID1)
Console.WriteLine(fileID2)

Output

6856
3667

This is superior to your method if you know the design of the data at design-time, because you get strong typing. Compare

Dim FileID = read.Item("files")

to

Dim fileIDs = rootobject.files.First().id

and see that in my example files is a concrete property of the object, while in yours files is a variable string you use to index a property which returns a JToken

Anyways I think you mainly had an issue with expecting a single value when an array was returned, which would be an issue in either case but with serialization you are notified by the compiler instead of at run-time.