Lets say you need to print some pages from a PDF file. But you don’t need to print the whole file, just a specific range, say pages 3 to the end of the document.

And let’s say you DON’T have any of those handy (and expensive) PDF libraries available. But of course you do have Acrobat Reader.

And let’s say you’ve got a whole pile of these PDFs that you need to get printed.

What to do?

First with the Printing

A little digging turned up that the AcroRd32.exe application (that actual Adobe Reader app, at least for version 9.x) can be invoked with command line parameters to print a file and exit:

AcroRd32.exe /p /h “filenamehere.pdf”

It’ll print to the current default printer, but that’s good enough for me for this purpose.

Simple enough, but you can’t specify which pages to print.

The Secret Ingredient

I’d almost given up on this when I came across a very handy utility called the PDFToolkit, by Sid Steward. PDFTK is a very small, free, command line driven utility. It won’t print, but it can slice and dice a PDF (or multiple PDFs) just about any which way you can dream up.

Say you have a PDF called input.pdf

You want to print pages 3 to the end of the file.

So, invoke PDFTK like so:

PDFTK.exe A=input.pdf cat A3-end output scratchfile.pdf

and then invoke the AcroRd32.exe line from above on the resulting scratchfile.pdf, and presto, your pdf is printed minus the first two pages!

Granted, if you’re developing a commercial product (or really even an inhouse utility), you’ll be much better served shelling out (no pun intended) a few bucks for a decent PDF library.

But in a pinch, PDFTK and AcroRd32 can be a pretty powerful little combination.

If you’ve used the Excel object model, youmay have discovered how incredibly handy the SaveCopyAs function is. Essentially, it allows you to save a currently loaded Excel spreadsheet into some arbitrary file, without altering the state of the loaded copy. In other words, if the user has altered the spreadsheet loaded into Excel, but hasn’t saved it, after a "SaveCopyAs”, that copy of the sheet is still considered dirty, and the saved file on disk does not have the user’s changes saved within it.

This is a very wonderful thing!

Basically, it means you can save off the spreadsheet as it currently exists in memory, complete with all the users edits up to this point, perform any operation on that saved copy that you want, and then either keep that copy or throw it away, and the copy that the user is currently working on is not affected in anyway whatsoever!

Good stuff.

But Word has never had it!

I’d rectified this long ago, in VB6, but recently had a need for this capability again, in VB.net this time.

Turns out, it’s incredibly simple to implement with VB.net, and much more intuitive to.

With .net 3.5, you can even create the function as an Extension Method, and directly add it to the Word Document object interface! Very cool!

The thing is, I knew I’d done this before, but couldn’t remember exactly how. After quite some time googling this, I came across a post where it was theorized it might be possible to implement SaveCopyAs by using the Compare function in Word.

Hmm, I’d never even tried the Compare, but it sounded interesting. After a few false starts, I ended up with this:

          

            Imports System.Runtime.CompilerServices

          

<System.Runtime.CompilerServices.Extension()> _ PublicSub SaveCopyAs(ByVal Document As Word.Document, ByVal FileName AsString)
Document.Compare(Name:=Document.FullName, CompareTarget:=Microsoft.Office.Interop.Word.WdCompareTarget.wdCompareTargetNew) With Document.Application.ActiveDocument If .Revisions.Count
> 0 Then .Revisions.RejectAll() .SaveAs(FileName, AddToRecentFiles:=False)
.Close() EndIfEndWith Document.Activate() End Sub

        

Notice that I’m using the CompilerServices.Extension attribute to flag this as an extension method. This is what adds this method directly to the Word Document object and makes it so much more intuitive to use.

Essentially, the idea here is to:

1. Compare the version of the document loaded in memory to the last saved version out on disk.
2. Write the comparison result to a new document in memory (i.e. what becomes the active document)
3. Check the revision count.
4. If there are revisions, you know there’s been changes made to the document since it was last saved, so Reject all the revisions, save the active document and close it.
5. If there were no revisions, the user hasn’t made any changes to the document since the last time they saved, so there’s really nothing else to do.
6. Reactivate the user’s originally active document

The real trick here was step 4. Originally, I was accepting the revisions and then saving, and it wasn’t working at all. Eventually I traced the problem back to the comparison order. It turns out, when you perform a compare to another file from a loaded Document object in Word, the results of the comparison are the changes required to convert from the version of the document you currently have open in Word to the other document.

So, if the user has added the word “Nostradamus” in a paragraph, then the comparison would yield a revision that says, essentially, “remove the word Nostradamus from this paragraph”. This is exactly backward from the behavior you want. Turns out that all I had to do was “Reject all changes” instead.

Believe it or not, this works a dream.

But…

I can’t imagine that performing a compare, especially on a large document, is going to be a particularly speedy process and I knew I’d done this before using a alternate interface that the Word Document object implemented, albeit undocumentedly so. I just couldn’t remember how…

Suffice it to say, eventually I stumbled across the long forgotten interface. That interface is the COM IPersistFile. It’s a basic interface COM typically uses when saving Structured Storage documents, which are what Word files usually are (though, fortunately, it works with Word 2007 for saving DOCX style files).

Turns out the Word Document object implements that interface. They just don’t make that fact common knowledge.

Using it is trivially easy, especially given that it’s a COM interface that the .net framework happens to define natively (though do note, you’ll need to Import the InteropServices.ComTypes Namespace as show below.

          

Imports System.Runtime.CompilerServices

Imports System.Runtime.InteropServices.ComTypes

          

<System.Runtime.CompilerServices.Extension()> _ PublicSub SaveCopyAs(ByVal Document As Word.Document, ByVal FileName AsString) Dim pf
= DirectCast(Document, IPersistFile)   


pf.Save(FileName, False) 'pf.SaveCompleted(FileName) End Sub

        

About that last commented line, that calls the SaveCompleted function. From the docs, it sounds like that is necessary, but I’ve never found a situation where it made a difference calling it or not.

Maybe someone can illuminate that aspect of the interface better than me?

But at any rate, the IPersistFile method is likely to be many times faster than the Compare method, especially for large files or files that the user has made many changes to without saving. Still, I thought the Compare method was interesting enough to warrant a mention.

So there you have it. SaveCopyAs for Word, implemented as an extension method that directly extends the Word Document object.

Yet more VB.net sweetness!

I ran into a very peculiar problem several days ago. Essentially, I had a class, with a few properties. One of those properties had some initialization code for a backing variable, like so:

          Public
          Property Count() AsIntegerGetReturn _count EndGetSet(ByVal Value AsInteger)
_count = Value EndSetEndPropertyPrivate _count AsInteger =
_collection.Count 

Now, granted, this is a little contrived. But the idea is that this particular property is initialized with a value from a private object (the _collection variable), that is set up during the constructor.

The problem was that the app was throwing an object not initialized when try to initially set the _count variable’s value.

This completely threw me. How on earth was my constructor not being called? After some debugging, I quickly discovered that the constructor is called after all these private variable initialization lines are executed! Now, that doesn’t really make a whole lot of sense, but, it’s what’s happening.

Only later did I come across this post by Patrick Steele. He’s got a great explanation and description of what’s happening there, so I won’t repeat that.

But the key to the whole issue is a quote by him from the Visual Basic Language Specification:

When a constructor's first statement is of the form MyBase.New(...), the constructor implicitly performs the initializations specified by the variable initializers of the instance variables declared in the type. This corresponds to a sequence of assignments that are executed immediately after invoking the direct base type constructor. Such ordering ensures that all base instance variables are initialized by their variable initializers before any statements that have access to the instance are executed.

(The emphasis is Patrick’s)

He goes on to quote the relevant part of the C# spec, which explicitly states exactly the opposite behavior for it’s initializers and constructors!

I haven’t been able to find any quote as to why there's a difference in behavior, or more specifically, why on earth VB’s behavior in this case seems so wrong.

If anyone knows, please comment!

I ran into a little surprise a few days ago. With something as innocuous as the “Replace” function, of all things!

Now, Replace has been around since, well, forever. The basic function has always looked like this:

X = Replace(StringToSearch, StringToSearchFor, StringToReplaceWith)

No big deal. Used it for years.

So imagine my surprise when I got an “Object not set” error on a string variable that I’d just used Replace on! How could that be?

So I checked the variable value. It was, in fact, “Nothing".

Ok, So I rerun the code, stepping through. The variable starts out as a string containing some data, then gets trimmed, and the resulting string in empty (still a string, just containing no characters).

Then I perform a replace on it, and suddenly, the string is Nothing?!

So, I coded up the following little test snippet.

          

            Private
            Sub Test() Dim x
= "Test A B C" Debug.Print(Replace(x, "A", "Z")) 'Results
in "Test Z B C" Debug.Print(x.Replace("A", "Z")) 'also
results in "Test Z B C" x = "" x = x.Replace("A", "Z")
Debug.Print(x IsNothing) 'result
is false, (x stays "") x = "" x = Microsoft.VisualBasic.Replace(x, "A", "Z")
Debug.Print(x IsNothing) 'result
is true!?! x = "" x = Replace(x, "A", "Z")
Debug.Print(x IsNothing) 'Result
is true!?!EndSub
        

The first two results are exactly as expected. The search string is replaced with the replace string.

The next result, ALSO, is as expected. x starts out as an empty string. I perform a replace on it, and the result is, duh! an empty string! Now, for as long as I’ve known the Replace function, this has not been how it works.

But the next two results both result in FALSE, meaning the result of the String.Replace function and of the Microsoft.VisualBasic.Replace function is Nothing, and not an empty string!

Google It!

So I started googling. I turned up this bug report from .net 1.1.

The response from Microsoft is:

Posted by Microsoft on 5/18/2006 at 3:02 PM

Hi,
Thank you very much for reporting this issue. Unfortunately, VB had this behavior in previous version too and we can't change it due to backward compatibility problem.
Thanks,
VB Development Team.

“Can’t be!” I yelled. Well, ok, I didn’t yell, but I exclaimed heartily <g>.

So I fired up VB6 and wrote up another test program, then ran it.

You can see the VB supplied variable inspector tooltip as I hovered over the value of X after I’d just run the normal REPLACE function on it in the EXACT SAME WAY as I’m doing in VB.net.

I hate to burst bubbles, but X starts out as an empty string, I run the REPLACE function on it, and it ends up… wait for it… an empty string! Not a null/nothing variable.

Maybe it’s another weird edge case scenario that the VB Team is talking about there, but, come on! This has got to be THE SINGLE MOST COMMON invocation of Replace. Why on earth should it work differently from VB6 to VB.net?

And one other thing. String.Replace is part of the .net FRAMEWORK people. It has virtually nothing to do with VB6 and certainly, compatibility shouldn’t have been a concern there. May for the version in the VisualBasic namespace, but not that String.Replace. Weak!

Short version of the story

Be VERY CAREFUL of using either String.Replace or the Microsoft.VisualBasic.Replace functions.

If you DO need them (they have a nice case-insensitive switch, which makes them handy), write a wrapper function that deals with this VB.net bug (yeah, I went there <g>) so you won’t get bitten and end up with rash.

At my last job, we used Snagit exclusively for screen captures. It’s a great tool, but it’s a tad pricey for doing quick screenshots on your home machine.

Just today, I was at a new contract gig and needed to do some screenshots. There wasn’t anything decent already available so I went googling for a bit.

First up. I believe I’ve talked about Faststone Capture before and that’s one of the first hits I got. But after downloading the latest version, I discovered that they’ve gone to a paid version with a 30 day eval. Don’t get me wrong, Faststone is a good screen capture util, and you might want to give it a whirl, but in this case, I was looking for something small and free.

Next try. Struck Gold!

PicPick is a little freeware app from wiziple.net. Odd name, but for free, it’s one amazingly polished screen capture app.

Let’s see, what’s to love?

• It’s got a built in image editor for quick annotations.
• It can do full screen caps, region caps, window caps, freehand caps, you name it.
• It’s fast.
• It can save to several different image formats

and lastly…

It’s got a built in screen protractor! WTH!

If you need to do screencaps on a budget, definitely check this one out!

Luke Sampson’s put up a nice little site that’s all about custom color styles for Visual Studio (looks like most schemes support VS2005/2008 AND 2010!)

For example, the high rated scheme right now is WekeRoad:

Pick one and you can download the scheme right there. Very easy to get a custom scheme (or a good base for your own scheme) going quickly.

I tend to prefer something with a few less colors (I’m not keen on the circus look, no matter how muted), but some of these schemes look quite nice.

Finally, check out my post about programming fonts here for a good font comparison.