Can the ParentForm's Settings property be accessed from a constituent user control, in order to modify such a setting?

Question

It is not too difficult to make a Form's location persistent, so that it can be repositioned where it was on restart:

Private Sub FlatForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Location = My.Settings.Location
End Sub

Private Sub FlatForm_LocationChanged(sender As Object, e As EventArgs) Handles Me.LocationChanged
    My.Settings.Location = Location
End Sub

Private Sub FlatForm_Disposed(sender As Object, e As EventArgs) Handles Me.Disposed
    My.Settings.Save()
End Sub

However, I have a user control being placed on many of my apps, so I was thinking of intercepting the parent's according events, in order to automatically do this for them as a service.

For example for the Disposed event:

Private Sub MyUserControl_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    AddHandler ParentForm.Disposed, AddressOf ParentDisposed
End Sub

But I have no clue on how to access the parent form's Settings property in the handler:

Private Sub ParentDisposed(sender As Object, e As EventArgs)
    ?
End Sub

Surely I can not add My.Settings.Save() , because I do not want to save the user control's location, but the parent form's in its own folder.

Is this possible, or need I do this a completely different way?

Answer 1

Thanks to a comment by user Visual Vincent, this is a working solution.

If you have placed a user control on a Windows Form, you can have automatic form tracking including persistency between calls.

---

In the control's Load event, this property is retrieved and applied to the parent form. Note, that we are coding the control's event, not the client form's. This means, that the client form may already be shown (yes, even before the Load event finishes), depending on what you do in it. This means, that we should place the according code to the event's very top.

It might seem natural, that the parent's location should be updated and saved in the Disposed event, but upon arriving there, the reference to ParentForm is Nothing already. This is also true, if the parent's Disposed event is handled by the control via AddHandler . Instead, we must use the parent's intercepted LocationChanged event to track the form's movements and to keep our property up-to-date.

Private Sub MyControl_Load(sender As Object, e As EventArgs) _
    Handles MyBase.Load

    'Retrieve the parent form's Location setting and apply it.
    ParentForm.Location = My.Settings.Location

    'Intercept the parent's LocationChanged event, so that its Location
    'property can be updated.
    AddHandler ParentForm.LocationChanged, AddressOf ParentLocationChanged

    ...
End Sub

'This routine is called, when the parent form is moved. It is intercepted in
'order to update the application's Location setting.
Private Sub ParentLocationChanged(sender As Object, e As EventArgs)
    My.Settings.Location = ParentForm.Location
End Sub

It is in the control's Dispose event, in which the settings are stored, including the Location setting.

You may want to opt out of this and have the client only be saving its own settings.

'When done, the application's settings are saved.
Private Sub MyControl_Disposed(sender As Object, e As EventArgs) _
    Handles Me.Disposed

    My.Settings.Save()
End Sub

From now on, when such a control is placed on a Form control, it automatically also monitors its movements and stores the form's position persistently between two sessions.

Answer 2

Parent财产：

YourControle.Parent.Location