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Asked: 2026-05-11T07:06:44+00:00

I’m trying to use a loading overlay on top of a Windows form that

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I’m trying to use a loading overlay on top of a Windows form that adds a 50% opaque layer on top of a windows form with a loading GIF, while it does what it needs to do in a background thread. The overlay is a windows form that I’m drawing in the onPaint event.

The loading overlay works fine on multiple different form loads, but fails to work properly when summoned to ensure patience during a 30 second upload process (That Prints a Word Document to PDF, then uploads that PDF to a SQL Server). This upload collects some data from the form, puts it into an Object, then operates entirely on a background thread. The loading overlay will appear, show the first frame loading GIF, then just freeze. The onPaint is getting fired and the image frame is being updated, but it isn’t visible

Constructor sets the form to be UserPainted:

Sub New()     InitializeComponent()     SetStyle(ControlStyles.UserPaint Or ControlStyles.Opaque, True)  End Sub

Then, in the Form.Shown event the ImageAnimator.Animate method is called:

Private Sub LoadingOverlay_Shown(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Shown     If Not currentlyAnimating Then         ImageAnimator.Animate(animatedImage, AddressOf Me.OnFrameChanged)         currentlyAnimating = True     End If End Sub

The onFrameChanged Event Handler just Invalidates the form:

Private Sub OnFrameChanged(ByVal sender As Object, ByVal e As System.EventArgs)     'Force a call to onPaint     Me.Invalidate() End Sub

Then onPaint is overridden and does the drawing:

Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs)     MyBase.OnPaint(e)      'Get the next frame ready for rendering     ImageAnimator.UpdateFrames()      'Draw the next frame in the animation.     e.Graphics.DrawImage(Me.animatedImage, GetCenter(Me.animatedImage.Size))     TextRenderer.DrawText(e.Graphics, strStatus, Me.Font, GetTextLocation(Me.animatedImage.Size), Color.White, Color.Black)  End Sub

Finally, the ImageAnimator.StopAnimate method is called in the Form Closing event:

Private Sub LoadingOverlay_FormClosed(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed     If currentlyAnimating Then         ImageAnimator.StopAnimate(animatedImage, AddressOf Me.OnFrameChanged)         currentlyAnimating = False     End If End Sub

Here’s how the loading overlay is being called and closed:

Private Sub ShowLoadingOverlay()     If Not blnLoadingOverlayVisible Then          Me.Enabled = False          patience = New LoadingOverlay()         patience.Location = Point.Add(parent.PointToScreen(Me.Location), New Size(0, parent.ToolStrip.Height + parent.MenuStrip.Height))         patience.Size = Me.Size         patience.Show()         patience.BringToFront()          blnLoadingOverlayVisible = True      End If End Sub  Private Sub HideLoadingOverlay()     If blnLoadingOverlayVisible Then         'Close loading overlay'         patience.Close()         patience.Dispose()         patience = Nothing         Me.Enabled = True         blnLoadingOverlayVisible = False     End If End Sub
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  1. ‘some COM’ is relevant. You’ll hit COM’s apartment threading rulez. A COM object like Word must be created on an STA thread. Your main UI thread qualifies, it starts at Main() and it has the [STAThread] attribute. Any method calls you make on another thread are automatically marshaled by COM to the STA thread. Gumming up your animation.

    This isn’t easy to fix. You’d need a background thread that must be an STA thread as well, use Thread.SetApartmentState(). And pump a message loop, use Application.Run(). Getting your code started and exiting the loop is awkward, try using a form that overrides SetVisibleCore() so you can avoid making it visible.

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