By Robert Ellison. Updated on Thursday, November 12, 2015.
The Volume Shadow Copy Service (VSS) takes a snapshot of an NTFS drive at a point in time. The clever thing about VSS is that it doesn't copy anything — it starts with the assumption that nothing has changed and then keeps track of every change to the snapshot so only changes need to be stored.
From Windows Vista on it's possible to mount a shadow copy as a drive letter or share. ShadowTask is a command line tool that creates a VSS copy, mounts it as a drive and then runs a program or batch file. For example:
ShadowTask C V dostuff.bat
Creates a copy of C:, mounts it as V: and then runs dostuff.bat.
Let's say you want to copy a locked file — maybe some outlook personal folders. Dostuff.bat could contain:
The ZIP contains both 32 and 64 bit versions of the tool. You must use the version that matches your platform. ShadowTask supports Windows Vista and 7. XP doesn't support mounting a shadow copy so ShadowCopy will fail if you try to use it on XP. ShadowCopy must run as admin (elevated).
(Published to the Fediverse as:
Do useful things with the volume shadow copy service (VSS) #code#vss ShadowTask mounts a volume shadow copy to a drive letter using VSS and then lets you run a batch file (maybe to copy a locked file or backup the entire drive))
PdfScan is a simple tool for scanning pages into a PDF file. You can scan single pages from a flatbed scanner or several pages from a document feeder. The page size applies to both the scan and the page(s) added to the PDF.
I wrote PdfScan because I know I'm going to be scanning a lot of documents over the next couple of weeks. Previously I used a tool called ScanToPDF from O Imaging but their licensing pissed me off so much that I'd rather waste time reinventing the wheel than pay them for another copy.
This is a beta — it works with my scanner and my documents. There's no installer, so extract the ZIP file and run the EXE to use it. PdfScan requires the .NET 4.0 Framework. If you get an error when you run PdfScan.exe try installing .NET 4 and then run it again.
If enough people use this I'll make it a bit more friendly, add an installer and release it through Catfood. If you like it leave a comment below. If it doesn't work for you leave a comment or email me and I'll try to help.
(Update September 12, 2010: I've tided PdfScan up and released it through Catfood Software. Download from Catfood PdfScan.)
I've been going nuts trying to scan from the document feeder on my Canon imageClass MF4150. Everything worked as expected from the flatbed, no dice trying to persuade the ADF to kick in. I found some sample code but it was oriented towards devices that can detect when a document is available in the feeder. Evidently my Canon doesn't expose this and so needs to be told the source to use.
The way to do this is to set the WIA_DPS_DOCUMENT_HANDLING_SELECT property to FEEDER. You then read WIA_DPS_DOCUMENT_HANDLING_STATUS to check that it's in the right mode and initiate the scan. This did not work for toffee.
After much experimentation I discovered a solution. I had been setting device properties and then setting item properties before requesting the scan. Switching the order - item then device - made everything work.
Here's the function to scan one page:
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A few notes — XImage is a type from PDFSharp. I wrote this as part of a PDF scanner that I'll post next so the scanned images are saved and then loaded into an XImage for rendering to the PDF document. The magic numbers come from WiaDef.h in the Platform SDK. If the ADF is out of pages this method sets the return image to null and eats the exception. This is because the function is called repeatedly to scan in pages until the ADF is empty if _adf is true (otherwise it grabs one image from the flatbed).
If you've been banging your head against a wall trying to get WIA to work with a document feeder I hope this helps.
Catfood PdfScan 1.40 is a small bug fix release. PdfScan converts documents to PDFs with the help of a flatbed or automatic document feeder (ADF) scanner.
Scanning multiple pages into a PDF file
PdfScan is a simple tool for scanning pages into a PDF file. You can scan single pages from a flatbed scanner or several pages from a document feeder. The page size applies to both the scan and the page(s) added to the PDF.
I wrote PdfScan because I know I'm going to be scanning a lot of documents over the next couple of weeks. Previously I used a tool called ScanToPDF from O Imaging but their licensing pissed me off so much that I'd rather waste time reinventing the wheel than pay them for another copy.
This is a beta — it works with my scanner and my documents. There's no installer, so extract the ZIP file and run the EXE to use it. PdfScan requires the .NET 4.0 Framework. If you get an error when you run PdfScan.exe try installing .NET 4 and then run it again.
If enough people use this I'll make it a bit more friendly, add an installer and release it through Catfood. If you like it leave a comment below. If it doesn't work for you leave a comment or email me and I'll try to help.
(Update September 12, 2010: I've tided PdfScan up and released it through Catfood Software. Download from Catfood PdfScan.)
By Robert Ellison. Updated on Saturday, September 29, 2018.
After floundering a bit with the WPF Dispatcher I've come up with a simple way to make sure an event handler executes on the UI thread without paying the overhead of always invoking a delegate.
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This has the benefit (for me at least) of being very easy to remember. Hook up the event handler and then if there's a chance it could be called from a different thread wrap it using the pattern above. It's easier to read than an anonymous delegate and much faster than defining a specific delegate for the event in question.
I haven't tested the various methods to see which is the fastest yet… will get round to this at some point.
(Published to the Fediverse as:
Use WPF Dispatcher to invoke event handler only when needed #code#wpf#tips How to Invoke or BeginInvoke an event handler to the UI thread using the WPF Dispatcher.)
By Robert Ellison. Updated on Thursday, November 12, 2015.
5. Validation
The metadata required to use the like button looks like this:
[code:html]
[/code]
But the property attribute isn't valid html or xhtml. The “Open” Graph Protocol says that it's inspired by Dublin Core. DC manages to get by using the name attribute like any other meta tag - why can't Open Graph? It's not the worst problem but it just seems needlessly irksome. Facebook has published a presentation describing their design decisions. This would be great, but it's in that Lessig one word per slide style and so it's attractive but completely useless without the presenter.
4. Fragility
Facebook's documentation is frustratingly sparse. For example you need to specify the owner of the page using a Facebook ID, and once you've chosen a name for your profile this is hard to find. The information vacuum has been filled with many erroneous blog posts saying to use the name, or some number from a shared photo (the best source is http://graph.facebook.com/robert.ellison, substituting your own username). Once you've got the admin ID wrong, you can't correct it - the first admin specified is fixed forever. What happens if a site is hacked and a bad actor sets themselves up as the admin? Surely something like the Google Webmaster Tools authentication scheme could have been used instead?
3. Pages with more than one object
Describing the object being liked in the head element limits you to one object per page. For some sites this is perfect, but what about a blog where you have many posts on the home page? It would be useful to have a like button per post, pointing at the permalink for the post in question. I've worked around this by having a like button for the blog on the home page, and a like button for each post on the post pages. Not ideal. I'm using the iframe version of the gadget, possibly there's some more flexibility with the XBML variant.
2. Duplicating existing pages
Let's say you've spent the past couple of years building up a Facebook page for your site/band/blog/movie and have thousands of fans. When you click your new like button for the first time you create a whole new page. There's no way to tell the like button about the existing page or the existing page about the like button. You now have at least two pages to worry about managing and potentially many, many more. You're also starting from scratch on the ‘like’ count, so even if your brand is already popular on Facebook it's back to Billy no-mates for you.
I can't believe this won't be fixed at some point. As with admin authentication above there must be a better way to establish ownership of various objects in the social graph.
1. Vocabulary
For better or worse Facebook has the inexorable pull to start making the semantic web a reality. Given this, and that there are something like twenty-four thousand verbs in the English language it's time for more expressiveness than ‘like’. You also can't comment on the ‘liked’ item in your stream (yet) so no clarification or discussion is possible.
--
Having said all that, if you enjoyed this post please click the ‘like’ button above ;)
A good enough holiday read and nice to see Patterson return to a straight psychological thriller rather than the last few OpEds loosely wrapped with some plot.
Advanced .NET Debugging (Addison-Wesley Microsoft Technology Series) by Mario Hewardt
5/5
Comprehensive introduction to low level .NET debugging - when you need to fire up WinDbg to check out the state of the managed heap, or debug a crash dump from the field you'll find this book invaluable. I wish it had been available when I started figuring out how to use SOS.
The Complete Stories of J. G. Ballard by J.G. Ballard
5/5
Wonderful collection of all of Ballard's short stories. It's a huge book with surprisingly few duds. My favorites include The Illuminated Man, clearly the inspiration for The Crystal World, which includes meaning bombs like "It's almost as if a sequence of displaced but identical images were being produced by refraction through a prism, but with the element of time replacing the role of light." and The Ultimate City (which isn't using ultimate in the sense of being good...). I've read most of Ballard's novels but not many of the short stories before. They're well worth the time.
By Robert Ellison. Updated on Saturday, September 29, 2018.
When testing out a WPF app on XP I got an unhelpful XamlParseException error report.
I was a little puzzled because I was hooking up error reporting in App.xaml.cs:
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My error handler was attempting to create a XAML window to report the error, and evidently this was bombing out as well triggering the good doctor Watson. I added a MessageBox call instead and discovered that the XamlParseException was wrapping a FileFormatException and the stack trace indicated that the problem was with setting the icon for the window. After removing the icon the app started up fine. Weird.
It turns out that WPF chokes on a compressed 256x256 icon on XP and Vista (Windows 7 seems to cope fine). Saving the icon without compression fixes the problem. I use IcoFX and you can set this at Options -> Preferences -> Options -> Compress 256x256 images for Windows Vista. Of course the consequence is that the icon is a couple of hundred kilobytes larger.
(Published to the Fediverse as:
XamlParseException and 256x256 icons #code#xaml#wpf#wtf You can't use a compressed 256x256 icon with WPF but you can include an uncompressed version.)
I've spent the last day learning how to use OAuth and XAuth to post to Twitter. There are rumblings that Twitter will start to phase out basic authentication later this year, and more importantly you can only get the nice “via...” attribution if you use OAuth (for new apps, old ones are grandfathered in).
I coded up my own OAuth implementation, referring to Twitter Development: The OAuth Specification on Wrox and the OAuthBase.cs class from the oauth project on Google Code. Both are great references, but both fail with multibyte characters. The problem is that each byte needs to be separately escaped. OAuthBase.cs encodes characters as ints rather than breaking out the bytes and the Wrox article incorrectly suggests using Uri.EscapeDataString().
Here's a method to correctly encode parameters for OAuth:
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NoEncode chars is a list of the permitted characters:
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An impact of this encoding is that spaces must be encoded as %20 rather than plus. I was worried that each space would end up counting as three characters towards the 140 character limit. I tested this and it isn't true, so use HttpUtility.UrlEncode() to calculate the number of characters in the post OAuthUrlEncode() or similar to actually encode post parameter.
(Published to the Fediverse as:
Space and multibyte character encoding for posting to Twitter using OAuth #code#twitter#oauth#xauth How to encode spaces and multibyte characters when posting to Twitter via OAuth / XAuth.)
By Robert Ellison. Updated on Friday, February 24, 2017.
Juliet, Naked by Nick Hornby
3/5
Classic Hornby. It's fairly close to High Fidelity with it's themes of love and music obsession-ism and so feels slightly too comfortable but certainly worth a read if you're a fan. 3/24/2010 2:00:00 AM
The Girl with the Dragon Tattoo (Millennium, #1) by Stieg Larsson
3/5
Slow, but highly atmospheric mystery. The first half of the book is dedicated to setting the scene and then the pieces start to fit into place like a glacier melting. The pace makes the occasional punctuation of extreme sexual violence all the more shocking. Fun enough, so I'll probably read the rest of the trilogy and try to catch the film (which has to be a profoundly truncated version).3/22/2010 2:00:00 AM
Practical WPF Charts and Graphics by Jack Xu
4/5
Be aware that this book is 90% code, 5% mathematics and 5% explanation. This isn't a criticism, Dr. Xu builds up a complete charting library that includes 2D, WPF 3D and manual 3D methods. The mathematics covers the theory and practice of 2D and 3D transforms as well as techniques for smoothing, interpolating and trending data. It's a fast read to get a sense of the content and then a great reference work to dip back into as needed. 3/14/2010 3:00:00 AM
C# Design and Development: Expert One on One by John Paul Mueller
1/5
This book is just atrocious. Each section sells itself as providing all the information you need about a certain topic, then provides trivial and often incorrect or at least highly subjective details. A couple of examples:
The chapter on error handling makes the point that you should catch the most specific Exception possible, but then goes on to demonstrate catching a FormatException, a DivideByZero exception and then just System.Exception. The whole point is to avoid catching Exceptions that you can't handle. There's a legitimate debate here between trying to plaster up the cracks with general catches and letting the application die with a useful stack, however this book doesn't discuss it. There's also very brief coverage of creating your own derived Exception but it doesn't touch on serialization.
Serializing an XML file is somehow included in the section on "Special Coding Methodologies", and labors over calling both .Flush() and .Close() on a StreamWriter. Despite the fact that you only need to call Close(), and that StreamWriter is IDisposable and so a using statement is really the way forward for this example.
I could go on, but won't. Avoid. 3/8/2010 2:00:00 AM
