Imports System

Imports System.Linq

Imports System.Collections

Imports System.Collections.Generic

Imports System.Data

Imports System.IO

Imports System.Globalization

Imports System.Reflection

Imports System.ComponentModel.DataAnnotations

Imports System.Xml.Linq

Imports System.Xml

Imports Microsoft.VisualBasic

Imports System.ComponentModel

Imports System.Collections.Specialized

Imports System.Collections.ObjectModel

Imports System.Runtime.CompilerServices

​

Imports Newtonsoft.Json

Imports Newtonsoft.Json.Linq

Imports Newtonsoft.Json.Converters

Imports Newtonsoft.Json.Serialization

​

Imports NUnit.Framework

​

    ' https://stackoverflow.com/questions/68983715/newtonsoft-json-deserializing-custom-collection-and-add-handler

Public Class ObservableCollectionAdvanced(Of T As INotifyPropertyChanged)

    Implements IEnumerable(Of T)

    Implements INotifyPropertyChanged

    Implements INotifyCollectionChanged

    Implements INotifyCollectionItemPropertyChanged 

​

    Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged

    Public Event CollectionChanged As NotifyCollectionChangedEventHandler Implements INotifyCollectionChanged.CollectionChanged

    Public Event CollectionItemPropertyChanged As PropertyChangedEventHandler Implements INotifyCollectionItemPropertyChanged.CollectionItemPropertyChanged

​

    Private ReadOnly _collection As New ObservableCollection(Of T)

​

    Public Sub New()

        Me.New(Enumerable.Empty(Of T)())

    End Sub

    Public Sub New(Items As IEnumerable(Of T))

        ' TODO: Decide whether to add the items before or after binding the event

        For Each i in Items

            If i IsNot Nothing Then

                _collection.Add(i)

            End If

        Next

        AddHandler _collection.CollectionChanged, Sub(sender As Object, e As NotifyCollectionChangedEventArgs)

                                                      RaiseEvent CollectionChanged(Me, e)

                                                  End Sub

    End Sub

​

    Default Public ReadOnly Property Item(Index As Integer) As T

        Get

            If Index >= 0 AndAlso Index < _collection.Count Then

                Return _collection(Index)

            Else

                Return Nothing

            End If

        End Get

    End Property

​

    Public Sub Add(Item As T)

        If Item IsNot Nothing Then

            Me.AddHandlerToItem(Item)

            _collection.Add(Item)

        End If

    End Sub

​

    Private Sub AddHandlerToItem(Item As T)

        If Not TypeOf Item Is INotifyPropertyChanged Then Exit Sub

        AddHandler DirectCast(Item, INotifyPropertyChanged).PropertyChanged, AddressOf Item_PropertyChanged

    End Sub

​

    Private Sub Item_PropertyChanged(sender As Object, e As PropertyChangedEventArgs)

        RaiseEvent CollectionItemPropertyChanged(sender, e)

    End Sub

​

    Public Function GetEnumerator() As IEnumerator(Of T) Implements IEnumerable(Of T).GetEnumerator

        Return _collection.GetEnumerator()

    End Function            

​

    Private Function GetEnumerator1() As IEnumerator Implements IEnumerable.GetEnumerator

        Return Me.GetEnumerator()

    End Function

End Class

​

' This interface was not included in the question so this is just a guess

Public Interface INotifyCollectionItemPropertyChanged

    Event CollectionItemPropertyChanged As PropertyChangedEventHandler

End Interface

​

Public Interface IDevice 

    Inherits INotifyPropertyChanged  

End Interface

​

Class TorsionArmDevice 

    Implements IDevice

​

    Public Event PropertyChanged As PropertyChangedEventHandler _  

        Implements INotifyPropertyChanged.PropertyChanged  

​

    Private Sub NotifyPropertyChanged(<CallerMemberName()> Optional ByVal propertyName As String = Nothing)  

        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(propertyName))  

    End Sub  

End Class

​

Public Module TestClass 

    Friend Sub Test()

        Dim devices As New ObservableCollectionAdvanced(Of IDevice)

        devices.add(new TorsionArmDevice())

        Dim JsonString as string = JsonConvert.SerializeObject(devices, Newtonsoft.Json.Formatting.Indented, New JsonSerializerSettings With {.TypeNameHandling = TypeNameHandling.All})

​

        Console.WriteLine(JsonString)

​

        Dim newDevices = Newtonsoft.Json.JsonConvert.DeserializeObject(of ObservableCollectionAdvanced(Of IDevice))(JsonString, New JsonSerializerSettings With {.TypeNameHandling = TypeNameHandling.All})

        Assert.AreEqual(devices.Count, newDevices.Count)

    End Sub 

End Module

​

Public Module Module1   

    Public Sub Main()

        Console.WriteLine("Environment version: " & Environment.Version.ToString())

        Console.WriteLine("Json.NET version: " & GetType(JsonSerializer).Assembly.FullName)

        Console.WriteLine("")

​

        Try

​

            TestClass.Test()

​

        Catch ex as Exception

​

            Console.WriteLine("Unhandled exception: ")

            Console.WriteLine(ex)

            Throw

​

        End Try

​

    End Sub 

End Module

​

​