Simple code that makes a picturebox visible and not visible

[szlamany]

I was using this code to make a picturebox not visible and then visible - picturebox is called MainWindow

    Private Sub TSToggle_Click(sender As System.Object, e As System.EventArgs) Handles TSToggle.Click
        Debug.WriteLine(MainWindow.Name)
        Debug.WriteLine(MainWindow.Visible)
        MainWindow.Visible = Not MainWindow.Visible
    End Sub

After I fill the picture box - via a drag and drop operation - I can no longer toggle it - I get a meaningless error

"Parameter is not valid." - which I show in the screen shot below. I also show the form document outline. PB is inside a content panel. What am I making "invalid" about the PB that it does not want to show up??

Even changed it to this - still got same error message!!

    Private Sub TSToggle_Click(sender As System.Object, e As System.EventArgs) Handles TSToggle.Click
        If PBInFront Then
            PBInFront = False
            MainWindow.SendToBack()
        Else
            PBInFront = True
            MainWindow.BringToFront()
        End If
    End Sub

[dunfiddlin]

This what happens when you make code up as you go along! .Visible has two values, True or False.

You also can't send a control to the back if there's nothing for it to be behind.

[MattP]

Not sure what's going on in your code. Just ran this on a blank project and it worked just fine.

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        TestPictureBox.Image = Image.FromFile("C:\Temp\round-error.png")
    End Sub

    Private Sub ToggleVisibilityButton_Click(sender As Object, e As EventArgs) Handles ToggleVisibilityButton.Click
        TestPictureBox.Visible = Not TestPictureBox.Visible
    End Sub

[szlamany]

This what happens when you make code up as you go along! .Visible has two values, True or False.

You also can't send a control to the back if there's nothing for it to be behind.

I have something for it to be behind. You can see that from the document outline. UIList is what is toggling in and out...

This code has been working for a year - it's in a proof-of-concept app we are working on.

Argh...

[MattP]

Oops just read that it stops working once you do a drag and drop on it. This works for me after doing a drag and drop.

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        TestPictureBox.AllowDrop = True
    End Sub

    Private Sub ToggleVisibilityButton_Click(sender As Object, e As EventArgs) Handles ToggleVisibilityButton.Click
        TestPictureBox.Visible = Not TestPictureBox.Visible
    End Sub

    Private Sub TestPictureBox_DragDrop(sender As Object, e As DragEventArgs) Handles TestPictureBox.DragDrop
        Dim pb = CType(sender, PictureBox)
        pb.Image = Image.FromFile(CType(e.Data.GetData(DataFormats.FileDrop), String()).First)
    End Sub

    Private Sub TestPictureBox_DragEnter(sender As Object, e As DragEventArgs) Handles TestPictureBox.DragEnter
        e.Effect = If(e.Data.GetDataPresent(DataFormats.FileDrop), DragDropEffects.Copy, DragDropEffects.None)
    End Sub

[szlamany]

I am chasing my tail here - it's a multi-threaded app so I could be seeing error's from elsewhere too.

Wow - I wish I could pinpoint exactly when this started happening.

Any interesting debugging idea's or trick's someone might have???

[Shaggy Hiker]

One question: Is the error always when the PB transitions in a specific direction? For instance, does it only occur when going from visible to not visible or the other way around?

If it is always in one direction and not the other, then that would suggest that you might be asking, "What is it about a PB with Visible = False that is not valid?" After all, I would expect that the problem had to do with the not visible state.

[szlamany]

I thought it was both directions - but now it seems like it might be when going from VISIBLE to going to NOT VISIBLE.

But that could be because I'm suppressing some TIMER code from drawing in the PB if it's not visible. That's new code - since I'm thinking my threads are misbehaving (although I'm synclocking and delgating everything the way I should)

[Shaggy Hiker]

It doesn't sound like a synchronization issue, exactly. I also think that the location of the exception may be a redd herring. The actual exception may be in something triggered by changing the visibility state, perhaps. I have no suggestion as to what that is, though, so it seems like it might be something specific to the code. Still, if you think that the behavior changed when you disabled a timer, that would be something worth looking into. The point is that if you can cause the behavior to change by taking some action, even if you don't know why that action would change the behavior, that would be a valuable clue as to where the problem lies.

Does toggling the visibility cause any intentional side effect in the code? For instance, does something occur as a result of the visibility changing? You already suggested that the behavior of some timer tick event changes behavior due to the visibility changing, are there other things?

Another thing that would be worth looking into, potentially, is how the visibility affects the control. The control may not be accessible in that state from some other code, though again, I can't say what. Some research into what ramifications Control.Visible = False has on the accessibility of the control might suggest something.

[Niya]

Close Visual Studio and delete the bin and obj folders that reside in the application project's folder. Re-open Visual Studio and compile/run the program again. Usually when I get weird errors I can't explain, I do that. Try it.

[szlamany]

@niya - I will try - maybe not tonight - too late...

But I did find some info on a exception trace that might indicate it's on some paint event of the picturebox - and even that it's thread related... Thing is I don't have any paint events in the code - it's way simpler than that!

   at System.Drawing.Image.get_Width()
   at System.Drawing.Image.get_Size()
   at System.Windows.Forms.PictureBox.ImageRectangleFromSizeMode(PictureBoxSizeMode mode)
   at System.Windows.Forms.PictureBox.OnPaint(PaintEventArgs pe)
   at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer)
   at System.Windows.Forms.Control.WmPaint(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at System.Windows.Forms.NativeWindow.DefWndProc(Message& m)
   at System.Windows.Forms.Form.DefWndProc(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WmSysCommand(Message& m)
   at System.Windows.Forms.Form.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
   at System.Windows.Forms.NativeWindow.DefWndProc(Message& m)
   at System.Windows.Forms.Form.DefWndProc(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.ContainerControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WmNcButtonDown(Message& m)
   at System.Windows.Forms.Form.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
   at UI.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
   at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

[Niya]

I donno if this could help but that error is occurring because GDI+ is failing to get the width from the native image:-

'
Public ReadOnly Property Width As Integer
    Get
        Dim num As Integer
        Dim status As Integer = Gdip.GdipGetImageWidth(New HandleRef(Me, Me.nativeImage), num)
        If (status <> 0) Then
            Throw Gdip.StatusException(status)
        End If
        Return num
    End Get
End Property

Changing the visibility triggers a redraw which ultimately leads to a call to the above. Its trying to get the width of the PictureBox's image and the above property is called. status is most likely not returning zero which causes an exception to be thrown:-

'
Friend Shared Function StatusException(ByVal status As Integer) As Exception
    Select Case status
        Case 1
            Return New ExternalException(SR.GetString("GdiplusGenericError"), -2147467259)
        Case 2
            Return New ArgumentException(SR.GetString("GdiplusInvalidParameter"))
        Case 3
            Return New OutOfMemoryException(SR.GetString("GdiplusOutOfMemory"))
        Case 4
            Return New InvalidOperationException(SR.GetString("GdiplusObjectBusy"))
        Case 5
            Return New OutOfMemoryException(SR.GetString("GdiplusInsufficientBuffer"))
        Case 6
            Return New NotImplementedException(SR.GetString("GdiplusNotImplemented"))
        Case 7
            Return New ExternalException(SR.GetString("GdiplusGenericError"), -2147467259)
        Case 8
            Return New InvalidOperationException(SR.GetString("GdiplusWrongState"))
        Case 9
            Return New ExternalException(SR.GetString("GdiplusAborted"), -2147467260)
        Case 10
            Return New FileNotFoundException(SR.GetString("GdiplusFileNotFound"))
        Case 11
            Return New OverflowException(SR.GetString("GdiplusOverflow"))
        Case 12
            Return New ExternalException(SR.GetString("GdiplusAccessDenied"), -2147024891)
        Case 13
            Return New ArgumentException(SR.GetString("GdiplusUnknownImageFormat"))
        Case 14
            Return New ArgumentException(SR.GetString("GdiplusFontFamilyNotFound", New Object() { "?" }))
        Case 15
            Return New ArgumentException(SR.GetString("GdiplusFontStyleNotFound", New Object() { "?", "?" }))
        Case &H10
            Return New ArgumentException(SR.GetString("GdiplusNotTrueTypeFont_NoName"))
        Case &H11
            Return New ExternalException(SR.GetString("GdiplusUnsupportedGdiplusVersion"), -2147467259)
        Case &H12
            Return New ExternalException(SR.GetString("GdiplusNotInitialized"), -2147467259)
        Case &H13
            Return New ArgumentException(SR.GetString("GdiplusPropertyNotFoundError"))
        Case 20
            Return New ArgumentException(SR.GetString("GdiplusPropertyNotSupportedError"))
    End Select
    Return New ExternalException(SR.GetString("GdiplusUnknown"), -2147418113)
End Function

When status is 2 it would throw an invalid parameter type exception which is most likely the exception you're getting. Hopefully, this will give you some kind of clue where to look. The error may have something to do with the image itself.

[szlamany]

@niya - I didn't see this post until now - thanks for this info!

How did you get the source of WIDTH and STATUSEXCEPTION??

[Niya]

.Net Reflector

[szlamany]

.Net Reflector

Thanks - just purchased .NET Reflector VSPro!