How to dispose of a particular instance of a class?

Sonhospa

Hello, this might be a dummy question, but I couldn't find a good answer on the internet yet. In my code I populate a CheckedListBox with the filenames of a particular filetype. If one of the entries gets checked ('ItemCheck' event of the CheckedListBox), I create an instance of a class that represents one of the relevant files.

	If ctrl.GetItemCheckState(ctrl.SelectedIndex) = 0 Then
		' create a new cfgFile class AND add it to the classes list
		ff = New cfgFile(ctrl.SelectedItem)
		lbl\_FileMessage.Text &= ff.Message
	Else
        ' How to dispose of the correct instance?
    End if

How can I properly dispose of the correct classes' instance, once the item is unchecked again? I thought about looping through the instances and check for their 'filename' property... but there doesn't seem to be a collection of instances, which I can refer to in a loop. Thank you for your advice, Mick

Michael_Davies

Where are you holding the created instances and how are they referenced to a particular line in the list box?

Sonhospa

Hi Michael, I guess that's part of my question... I tried to put every newly created class into a List(of class), where I could add/remove entries. But removing elements from the list (i.e. list.count resulted in -1) didn't dispose of their instances (static counter variable, decremented inside the 'dispose' method, stayed the same). Thank you for guiding me further.

Sonhospa

Would that be a probable solution?

Public Class cfgFiles
Inherits SortedList(Of String, cfgFile)

Private Shared files As New SortedList(Of String, cfgFile)

Public Overloads Shared Sub Add(ByVal fileName As String)
	files.Add(fileName, New cfgFile(fileName))
End Sub

Public Overloads Shared Sub Remove(ByVal fileName As String)
	Dim ff As cfgFile = files(fileName)
	ff.Dispose()
	files.Remove(fileName)
End Sub

Public Overloads Function GetEnumerator() As IEnumerator(Of cfgFile)
	Return files.GetEnumerator
End Function

Public Property SelectedItem As cfgFile
Default Public Overloads Property Item(index As Integer)
	Get
		SelectedItem = files(index)
		Return SelectedItem
	End Get
	Set(value)	' as cfgFile?
		files(index) = value
	End Set
End Property

End Class

Lost User

Memory allocated in .NET using the new command can automatically claimed by the GC as soon as the object loses scope. I say can, because it won't do it immediatly. Disposing is only required if there are unmanaged resources owned by the object. Which means you can safely remove the "ff.Dispose()" statement. Also see Object.Finalize Method (System)[^], Garbage Collection[^] and Implementing a Dispose Method[^].

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^][](X-Clacks-Overhead: GNU Terry Pratchett)

Sonhospa

Thank you for this insight, Eddy. Still I am confused having the list.count variable reduced after removing the list entry (which is an instance), but the instance itself seems to be still alive (shared counter variable of the class doesn't decrement).

Lost User

That is because it still is alive. It will remain so until the GC collects it. You can't "force" it to be deleted from memory.

Bastard Programmer from Hell :suss: If you can't read my code, try converting it here[^][](X-Clacks-Overhead: GNU Terry Pratchett)