Actually I have tried to specifically dispose all objects where and whenever possible (even though they are destroyed anyway as soon as the scope they are in is completed) but it makes no difference. The WebBrowser object is created within code and it works fine for me:

WebBrowser x = new WebBrowser();
x.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(webBrowser_DocumentCompleted);
x.Navigate("http://www.somesite.com");

Anyways, I have concluded my quest for solution with the conclusion that multiple WebBrowser objects running simultaneously simply create some problems in the underlying framework (IE) that, and at some point (too many simultaneous WebBrowser objects/requests as it's possible in web-server environment), can result in unexpected results. And, that this issue can't be solved from within the calling code.

I managed to get the WebBrowser to work off screen too, I'm not sure what fixed it though. I totally buy that multiple WebBrowser controls will cause problems too, makes sense.

However, calling Dispose() explicitly is actually very important. Simply going out of scope isn't good enough, calling dispose will clear up any unmanaged resources and simply going out of scope will cause the GC to only clean up managed resources. It is VERY important to always call dispose on an object implementing IDisposable. Wrap it in a using(IDisposable d = ...) { ... } to make your life easier (so dispose will still get called if there is an exception).

As I said, I tried disposing all possible objects - but with no difference to the outcome. Disposing gets rid of the no-longer-used objects, but in my case the problem lies in objects working at the same time in different threads - that somehow results with a conflict in the underlying framework level (odd as it may be).

That's unfortunate but doesn't surprise me. I suppose the logical conclusion would be to have a single WebBrowser control that does all of the rendering then queue the requests and asynchronously render the images and pass them back to the requestors. A lot more work but it's worth it if it fixes bugs that take down the system. 

Have used this Code for a long time with multiple weBrowser controls without problems but recently I've noticed that FLASH, SIlverlight and other stuff are not being thumbnailed.  While most of the standard HTML shows up the newer stuff shows as black spots in the case of FLASH and Styler-sheets with xml, Sliverlight just ends up showing the background color.  Standard HTML works fine!
Does the DOM/IHTMLELEMENT not carry these nodes or items?  Are they carried somewhere else?
ANY HELP GREATLY APPRECIATED!

MY VERSION of CODE BELOW     VS2005/Net 2.0 - VB.net

Public Enum TernaryRasterOperations
    SRCCOPY = &HCC0020       ' dest = source
    SRCPAINT = &HEE0086      ' dest = source OR dest
    SRCAND = &H8800C6        ' dest = source AND dest
    SRCINVERT = &H660046     ' dest = source XOR dest
    SRCERASE = &H440328      ' dest = source AND (NOT dest )
    NOTSRCCOPY = &H330008    ' dest = (NOT source)
    NOTSRCERASE = &H1100A6   ' dest = (NOT src) AND (NOT dest)
    MERGECOPY = &HC000CA     ' dest = (source AND pattern)
    MERGEPAINT = &HBB0226    ' dest = (NOT source) OR dest
    PATCOPY = &HF00021       ' dest = pattern
    PATPAINT = &HFB0A09      ' dest = DPSnoo
    PATINVERT = &H5A0049     ' dest = pattern XOR dest
    DSTINVERT = &H550009     ' dest = (NOT dest)
    BLACKNESS = &H42         ' dest = BLACK
    WHITENESS = &HFF0062     ' dest = WHITE
End Enum

<Guid("3050f669-98b5-11cf-bb82-00aa00bdce0b"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown), ComVisible(True), ComImport()> _
Interface IHTMLElementRender
Sub DrawToDC(<[In]()> ByVal hDC As IntPtr)

Sub SetDocumentPrinter(<[In](), MarshalAs(UnmanagedType.BStr)> _
  ByVal bstrPrinterName As String, <[In]()> _
  ByVal hDC As IntPtr)
End Interface

Public Sub Thumb()
        'Console.WriteLine("Public Class BrowserThumbnail-Public Sub Thumb|E-- ")
        Try
            Dim document As mshtml.IHTMLDocument2 = DirectCast(Myform2.Ax15Form2Browser.Document.DomDocument, mshtml.IHTMLDocument2)
            Dim element As mshtml.IHTMLElement2 = DirectCast(document.body, mshtml.IHTMLElement2)
            Dim render As IHTMLElementRender = DirectCast(element, IHTMLElementRender)
            Dim GraphicsObject As Graphics = Myform2.thumbScr15.CreateGraphics
            Dim PointerToGraphics As IntPtr = GraphicsObject.GetHdc
            Dim PointerToDC As IntPtr = CreateCompatibleDC(PointerToDC)
            Dim PointerToBitmap As IntPtr = CreateCompatibleBitmap(PointerToGraphics, ThumbCopyFromWT, ThumbCopyFromHT)
            SelectObject(PointerToDC, PointerToBitmap)
            render.DrawToDC(PointerToDC)
            GraphicsObject.ReleaseHdc(PointerToGraphics)
            Dim dummyCallBack As System.Drawing.Image.GetThumbnailImageAbort
            dummyCallBack = New System.Drawing.Image.GetThumbnailImageAbort(AddressOf ThumbnailCallback)
            Dim fullSizeImg As System.Drawing.Image
            fullSizeImg = System.Drawing.Image.FromHbitmap(PointerToBitmap)
            Dim URLfullSizeImg As System.Drawing.Image
            URLfullSizeImg = System.Drawing.Image.FromHbitmap(PointerToBitmap)
            Myform2.thumbScr15.Image = fullSizeImg.GetThumbnailImage(ThumbWidth, ThumbSizeHT, dummyCallBack, IntPtr.Zero)
            URLHistThumbImage15 = URLfullSizeImg.GetThumbnailImage(URLHistImageWD, URLHistImageHT, dummyCallBack, IntPtr.Zero)
            'Cleanup
            CType(GraphicsObject, IDisposable).Dispose()
            DeleteDC(PointerToDC)
            DeleteObject(PointerToBitmap)
            T15Done = True
        Catch ex As System.NullReferenceException
            Console.WriteLine("--- NullReferenceException ---" & "  " & _
            vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
            ' Code reacting to NullReferenceException
        Catch ex As Exception
            ' Code reacting to any exception
            Console.WriteLine(vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
        End Try

Greg,

 Unfortunately, the code is unable to capture Flash or Silverlight and I am not aware of any way around this.

Sorry, Alan

Hi Alan,

I’ve looked around a bit and no one has a solution.   I certainly can do a screen capture and thumbnail it that way; unfortunately this is a display and capture mechanism and I lose the benefit of thumb-nailing multiple browsers under the cover. 

Do you think it’s possible (under the cover) to navigate to a site, then somehow device context it upon browser completion and thumbnail it from a DC?

Well… maybe not.  If I find a way to do this I will certainly post it here.

Thanks Alan,

Greg

Hi Alan,

Found a timing bug in my project (browser completion was occurring before FLASH was completed) so FLASH now does work, but SilverLight and xsl/parser/xml HTML generated images do not. 

It was suggested via MSDN that IHTMLElementRender has problems (misses’ stuff) that could be resolved by using IViewObject’s Draw Function.  What I need is a VB.net example of the parameters required by IViewObject:Draw to draw [BELOW--- (DIM) Drawrender to a DC (device Context)].   I been searching all over to find an example but have had no luck…  Do you have a VB.net example?

Thanks Alan,  Greg

Imports Microsoft.VisualStudio.OLE.Interop

<Guid("0000010D-0000-0000-C000-000000000046")> <InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown), ComVisible(True), ComImport()> _
Interface IViewObject

    Sub Draw(ByVal dwDrawAspect As UInteger, _
    ByVal lindex As Integer, _
    ByVal pvAspect As UInteger, _
    ByVal ptd() As Microsoft.VisualStudio.OLE.Interop.DVTARGETDEVICE, _
    ByVal hdcTargetDev As UInteger, ByVal hdcDraw As UInteger, _
    ByVal lprcBounds() As Microsoft.VisualStudio.OLE.Interop.RECTL, _
    ByVal lprcWBounds() As Microsoft.VisualStudio.OLE.Interop.RECTL, _
    ByVal pContinue As Microsoft.VisualStudio.OLE.Interop.IContinue)

End Interface

Try
Dim document As mshtml.IHTMLDocument2 = DirectCast(Me.WebBrowser1.Document.DomDocument, mshtml.IHTMLDocument2)
Dim element As mshtml.IHTMLElement2 = DirectCast(document.body, mshtml.IHTMLElement2)
'Dim render As IHTMLElementRender = DirectCast(element, IHTMLElementRender)
Dim Drawrender As IViewObject = DirectCast(element, IViewObject)

Dim GraphicsObject As Graphics = Me.PictureBox1.CreateGraphics
Dim PointerToGraphics As IntPtr = GraphicsObject.GetHdc
Dim PointerToDC As IntPtr = CreateCompatibleDC(IntPtr.Zero)
Dim PointerToBitmap As IntPtr = CreateCompatibleBitmap(PointerToGraphics, Me.WebBrowser1.Width, Me.WebBrowser1.Height)

SelectObject(PointerToDC, PointerToBitmap)

DrawRender.Draw(?????...
'render.DrawToDC(PointerToDC)

I'd love to know the solution, as I'm in the same boat.  So if you do figure it out, please post back here to this thread!

The code I came up with is below.  However, it faults inside of the Draw call.  I'm really not sure if passing an "array of one RECTL" is the right way to handle this interface, which wants a pointer to a RECTL when you're writing it natively.

Rectangle rectDest = new Rectangle(new Point(0, 0), size);

while (_browser.ReadyState != WebBrowserReadyState.Complete)

_browser.DocumentText = aobjData[DataFormats.Html] as string;

IViewObjectEx viewObjectEx = _browser.Document.DomDocument as IViewObjectEx;

double xScale = (double)size.Width / (double)sizeDocument.Width;

SIZEL sizel;

// Save away the old size so we can restore it

oleObject.GetExtent(1, sizelOld); // DVASPECT_CONTENT == 1

rectl[0].right = size.Width + iPadding; // Extra padding so scrollbar renders outside thumbnail

Hi Dave I’m working on it.

I have a variation of the code that gets the WebBrowser control from its rendered address passed to the context of the rendered desktop window.  This means It works only if the WebBrowser control is displayed on the desktop in a form (Code Below) and it does not matter where the webBrowser control is on the desktop or what is in it XSL/XML, Silverlight whatever.  I am trying to figure out how the rendered desktop window gets passed the rendered HTML.

From code below:
BitBlt(AddrCreateCompatibleDC, 0, 0, WinWidth, WinHeight, GetWindowDC(Me.WebBrowser1.Handle), 0, 0, SRCCOPY)

StretchBlt(AddrOfPB1, 0, 0, 100, 100, AddrCreateCompatibleDC, 0, 0, Me.WebBrowser1.Width, Me.WebBrowser1.Height, TernaryRasterOperations.SRCCOPY)

Of course this is not what I want and for whatever reason I cannot figure out where the rendered HTML is being stored.  So now I am using WinDBG to go through the assembly to find out what address (buffer) all HTML for display are being rendered to before being posted to the screens context!   Once I figure this out I’ll write a callable assembler or C++ routine from any .Net language. 

I tried to go another route to see what the value of Webbrowse1.handle would be outside of NET so I Marshaled it from the outside back to NET – got the same result.  I’ve included the code if you want to play around with it.  To use the mshtml._RemotableHandle, a BitBlt call which I have commented out getRHandle(Me.WebBrowser1.Handle) You’ll need the following sub to grap it from outside of NET

-------
Public remotableHandle As mshtml._RemotableHandle

'This essentially stores the IntPtr into unmanaged memory and then marshalls it again into a new structure, in this case a _RemotableHandle. Can be used as follows:

    Public Function getRHandle(ByVal windowHandle As IntPtr)
        'Allocate unmanaged memory to store this IntPtr0
        Dim address As IntPtr = Marshal.AllocHGlobal(IntPtr.Size)

        'Write the IntPtr into unmanaged memory
        Marshal.WriteIntPtr(address, windowHandle)

        'Return the RemotableHandle by marshalling it from unmanaged memory
        Return Marshal.PtrToStructure(address, GetType(mshtml._RemotableHandle))
    End Function

--------------

    Private Structure RECT
        Dim Left As Integer
        Dim Top As Integer
        Dim Right As Integer
        Dim Bottom As Integer
    End Structure

Try
            'Handle for the desktop window
            Dim AddrDesktopWindow As IntPtr
            If AddrDesktopWindow = 0 Then AddrDesktopWindow = GetDesktopWindow

            'getWindow Size
            Dim rcWindow As RECT
            GetWindowRect(AddrDesktopWindow, rcWindow)
            Dim WinHeight As Integer = rcWindow.Right - rcWindow.Left
            Dim WinWidth As Integer = rcWindow.Bottom - rcWindow.Top

            Dim PB1 As Graphics = Me.PictureBox1.CreateGraphics
            Dim AddrOfPB1 As IntPtr = PB1.GetHdc

            Dim AddrOfPictureBox1 As IntPtr = Me.PictureBox1.Handle

            'create a compatible DC
            Dim AddrCreateCompatibleDC As IntPtr = CreateCompatibleDC(IntPtr.Zero)

            'create a memory bitmap in the DC just created, the size of the window we're capturing
            Dim AddrCreateCompatibleBitmap As IntPtr = CreateCompatibleBitmap(AddrOfPB1, WinWidth, WinHeight)

            'Prepare DC as a Bitmap using selectObject to configure the DC
            SelectObject(AddrCreateCompatibleDC, AddrCreateCompatibleBitmap)

            'copy the screen image into the DC
            'BitBlt(AddrCreateCompatibleDC, 0, 0, WinWidth, WinHeight, GetWindowDC(AddrDesktopWindow), 0, 0, SRCCOPY)
            BitBlt(AddrCreateCompatibleDC, 0, 0, WinWidth, WinHeight, GetWindowDC(Me.WebBrowser1.Handle), 0, 0, SRCCOPY)
            'BitBlt(AddrCreateCompatibleDC, 0, 0, WinWidth, WinHeight, getRHandle(Me.WebBrowser1.Handle), 0, 0, SRCCOPY)

            'Clone image of PictureBox1 to Picturebox2 when the IMAGE is in the Device Context
            '#### BitBlt(AddrOfPB1, 0, 0, WinWidth, WinHeight, AddrCreateCompatibleDC, 0, 0, SRCCOPY)
            StretchBlt(AddrOfPB1, 0, 0, 100, 100, AddrCreateCompatibleDC, 0, 0, Me.WebBrowser1.Width, Me.WebBrowser1.Height, TernaryRasterOperations.SRCCOPY)

            PB1.ReleaseHdc(AddrOfPB1)
            CType(PB1, IDisposable).Dispose()
            DeleteDC(AddrCreateCompatibleDC)
            DeleteObject(AddrCreateCompatibleBitmap)

        Catch ex As System.NullReferenceException
            MsgBox("--- NullReferenceException ---" & "  " & _
            vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
            ' Code reacting to NullReferenceException
        Catch ex As Exception
            ' Code reacting to any exception
            MsgBox(vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
        End Try
    End Sub

Thanks!  For my appliction the web browser control needs to be offscreen (not on a form), so it won't work for me.  I did find one thing interesting, though, which is the the interface definition for IViewObjectEx::Draw that ships in microsoft.visualstudio.ole.interop is wrong.  It's missing the last parameter (the DWORD value passed to the continuation function) from the definition of Draw.  So when you call it, its going to pop extra bytes off the stack before returning, and will crash.  Which it did, so I had to create my own interface definition (with the same guid) and that got it working.  That interface is below, in case it helps anyone.

I'm still having a problem that its not drawing anything into my DC, and that's where I'm at right now, debugging the Draw() implementation in mshtml to figure out why...

[Guid("3AF24292-0C96-11CE-A0CF-00AA00600AB8")]
[ComConversionLoss]
[InterfaceType(1)]
public interface IViewObjectExDave
{
void Draw(uint dwDrawAspect, int lindex, uint pvAspect, DVTARGETDEVICE[] ptd, uint hdcTargetDev, uint hdcDraw, RECTL[] lprcBounds, RECTL[] lprcWBounds, IContinue pContinue, uint x);
 

// etc, rest of methods
 

}

OK, I FINALLY GOT IT TO WORK…..OFFSCREEN with SilverLight and XSL/XML EXCEPT SHOCKWAVE FLASH!

At least I have a way to call Alan's routine when I detect a non-Flash HTML screen and now use IViewObject Draw when I have a Silverlight or xml/xsl css gened screen.  AGAIN all this works off Screen!

Unfortunately as far as I can tell IViewObject is incompatible with trying to DirectCast it down to the element as in Alan's code so, while I now have a dual solution (with some upfront HTML parsing) I will keep looking into a single step solution.

After looking at WinDbg and screwing around with memory addresses.  I finally got it to write off screen using IViewObject Draw function to a DC and then to a thumbnail.  What a pain this was!

I had to use StretchBlt to grab it from the DC to shrink it down to a 100 by 100 thumbnail.  I do not like the way StretchBlt renders it.  The thumbnail is grainy and not as clear as Alan’s original FromBitmap code.  BUT for NOW ENOUGH IS ENOUGH!  I’ll screw with that later… ( I now have replace StretchBlt see my next reply)

The Following CODE will write the rendered HTML screen from its memory location (not the form on the Desktop) and post it to a DEVICE COINTEXT.  It works WITH SILVERLIGHT and XSL/XML.  From the DC I use StretchBlt (will change that) to shrink it to the Picturebox 100 by 100 thumb.

<ComImport(), _
InterfaceType(ComInterfaceType.InterfaceIsIUnknown), _
Guid("00000127-0000-0000-C000-000000000046")> _
Public Interface IViewObject
    Function Draw(ByVal dwDrawAspect As Int32, _
    ByVal lindex As Int32, _
    ByVal pvAspect As IntPtr, _
    ByVal ptd As IntPtr, _
    ByVal hicTargetDev As Int32, _
    ByVal hdcDraw As IntPtr, _
    ByVal prcBounds As IntPtr, _
    ByVal prcWBounds As RectangleF, _
    ByVal fnContinue As IntPtr, _
    ByVal dwContinue As Int32) As Int32
End Interface

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Try

            Dim ViewObject As IViewObject = DirectCast(Me.WebBrowser1.Document.DomDocument, IViewObject)

            Dim PB1 As Graphics = Me.PictureBox1.CreateGraphics
            Dim AddrOfPB1 As IntPtr = PB1.GetHdc

            'create a compatible DC
            Dim AddrCreateCompatibleDC As IntPtr = CreateCompatibleDC(IntPtr.Zero)

            'create a memory bitmap in the DC just created, the size of the window we're capturing
            Dim AddrCreateCompatibleBitmap As IntPtr = CreateCompatibleBitmap(AddrOfPB1, Me.WebBrowser1.Width, Me.WebBrowser1.Height)

            'Prepare DC as a Bitmap using selectObject to configure the DC
            SelectObject(AddrCreateCompatibleDC, AddrCreateCompatibleBitmap)

            'Draw the Rendered DomDocument to the Device Context
            ViewObject.Draw(1, 1, Nothing, Nothing, 0, AddrCreateCompatibleDC, Nothing, Nothing, Nothing, 0)

            'Use StretchBlt to shrink it down to the Theubnail
            StretchBlt(AddrOfPB1, 0, 0, 100, 100, AddrCreateCompatibleDC, 0, 0, Me.WebBrowser1.Width, Me.WebBrowser1.Height, TernaryRasterOperations.SRCCOPY)

            'Dim fullSizeImg As System.Drawing.Image
            'fullSizeImg = System.Drawing.Image.FromHbitmap(AddrCreateCompatibleBitmap)

            PB1.ReleaseHdc(AddrOfPB1)
            CType(PB1, IDisposable).Dispose()
            DeleteDC(AddrCreateCompatibleDC)
            DeleteObject(AddrCreateCompatibleBitmap)

        Catch ex As System.NullReferenceException
            MsgBox("--- NullReferenceException ---" & "  " & _
            vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
            ' Code reacting to NullReferenceException
        Catch ex As Exception
            ' Code reacting to any exception
            MsgBox(vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
        End Try
  

End Sub

Ok just replace StretchBlt with.  Not sure why this was not working before?  other than I was up very late and just couldn't see straight..

Me.PictureBox1.Image = fullSizeImg.GetThumbnailImage(100, 100, Nothing, IntPtr.Zero)

Ok, this is the final version – and final comments.

IViewObjectDraw is now my standard.  When the HTML text is converted into a rendered image sitting in memory and available to be moved to the desktop form’s screen buffer for display, … for whatever reason IVewObject.Draw will do a better job of picking up all of the pieces at whatever addresses they are stored at giving me an off-screen image (using the screen’s device context) to thumbnail from. 

I now use the original  IHTMLElement.DrawToDc to pickup the only item (so far) the “Adobe Shockwave embedded player” the rest can be handled by IViewObject.Draw – flash, xsl/css, silverlight, etc.  It’s now a simple matter of searching the HTML document text looking for Adobe Shockwave and calling the original  IHTMLElement.DrawToDc.

It is kind of a pain to do it this way because I must pre-check for Shcokwave, but the overhead with some reduced instruction tricks is reasonable… Also IViewObject code seems faster

Greg

Public Sub IviewDrawStyleThumb1()
        Try
            Dim ViewObject As IViewObject = DirectCast(Myform2.Ax1Form2Browser.Document.DomDocument, IViewObject)

            Dim PB1 As Graphics = Myform2.thumbScr1.CreateGraphics
            Dim AddrOfPB1 As IntPtr = PB1.GetHdc

            'create a compatible DC
            Dim AddrCreateCompatibleDC As IntPtr = CreateCompatibleDC(IntPtr.Zero)

            'create a memory bitmap in the DC just created, the size of the window we're capturing
            Dim AddrCreateCompatibleBitmap As IntPtr = CreateCompatibleBitmap(AddrOfPB1, ThumbCopyFromWT, ThumbCopyFromHT)

            'Prepare DC as a Bitmap using selectObject to configure the DC
            SelectObject(AddrCreateCompatibleDC, AddrCreateCompatibleBitmap)

            'Draw the Rendered DomDocument to the Device Context
            ViewObject.Draw(1, 1, Nothing, Nothing, 0, AddrCreateCompatibleDC, Nothing, Nothing, Nothing, 0)

            Dim fullSizeImg1 As System.Drawing.Image
            fullSizeImg1 = System.Drawing.Image.FromHbitmap(AddrCreateCompatibleBitmap)
            Myform2.thumbScr1.Image = fullSizeImg1.GetThumbnailImage(ThumbWidth, ThumbSizeHT, Nothing, IntPtr.Zero)

            Dim URLfullSizeImg As System.Drawing.Image
            URLfullSizeImg = System.Drawing.Image.FromHbitmap(AddrCreateCompatibleBitmap)
            URLHistThumbImage1 = URLfullSizeImg.GetThumbnailImage(URLHistImageWD, URLHistImageHT, Nothing, IntPtr.Zero)

            PB1.ReleaseHdc(AddrOfPB1)
            CType(PB1, IDisposable).Dispose()
            DeleteDC(AddrCreateCompatibleDC)
            DeleteObject(AddrCreateCompatibleBitmap)

            T1Done = True

        Catch ex As System.NullReferenceException
            MsgBox("--- NullReferenceException ---" & "  " & _
            vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
            ' Code reacting to NullReferenceException
        Catch ex As Exception
            ' Code reacting to any exception
            MsgBox(vbCrLf & "Message --- " & ex.Message & "  " & _
            vbCrLf & "Source --- " & ex.Source & "  " & _
            vbCrLf & "StackTrace --- " & ex.StackTrace & "  " & _
            vbCrLf & "TargetSite --- " & ex.TargetSite.ToString)
        End Try

    End Sub