rebus

Lies, Damn Lies & MSDN Documentation

corrywht — Sat, 04 Apr 2009 02:27:54 +0000

The MSDN documentation for XmlDocument.LoadXml() states “This method does not do DTD or Schema validation. If you want validation to occur, use the Load method and pass it an XmlValidatingReader. See XmlDocument for an example of load-time validation”. As it turns out, this is only a half-truth.

If you happen to be dealing with XHTML (or any other standard that has a publicly accessible DTD), then you’ll most likely have a DOCTYPE declaration at the top of the document, like

However, if you try to load an XHTML document containing the DOCTYPE declaration into an XmlDocument object using LoadXml(), the underlying XmlTextReader will try to resolve the URIs in the DOCTYPE. This is usually fine in a development environment, but can cause major headaches when working in a restricted production environment, where, for example, the Web severs cannot access the Internet in general, or the W3C site in particular.

So, what do to?

Well, you have two options:

1. Set the XmlResolver object in the XmlDocument to null, i.e.

XmlDocument xdXhtmlContent = new XmlDocument();
xdXhtmlContent.XmlResolver = null;

2. Copy the DTD(s) locally and create your own XmlUrlResolver that overrides the URI for them (e.g. to a local path):

public class FileSystemDTDUriResolver : XmlUrlResolver
{
/// 
/// Resolves the absolute URI from the base and relative URIs.
/// 
/// The base URI used to resolve the relative URI.
/// The URI to resolve. The URI can be absolute or relative. If absolute, this value effectively replaces the baseUri value. If relative, it combines with the baseUri to make an absolute URI.
/// 
/// The baseUri and relativeUri are given to match the method signature of XmlUrlResolver. However, for the purpose of an XmlDocument's XmlResolver, the Uri cannot be relative.
public override Uri ResolveUri(Uri baseUri, string relativeUri)
{
if (relativeUri.ToLower().EndsWith(".dtd"))
{
string sRequestedDtd = relativeUri.Substring(relativeUri.LastIndexOf('/')).TrimStart('/');
string sDTDFilesLocation = ConfigurationManager.AppSettings["DTDFileSystemLocation"].Replace('\\', '/');    //C:\Webfiles\w3xml\DTD\
if (sDTDFilesLocation.LastIndexOf('/') != sDTDFilesLocation.Length - 1)
{
sDTDFilesLocation += "/";
}
return new Uri("file:///" + sDTDFilesLocation + sRequestedDtd);
}
return base.ResolveUri(baseUri, relativeUri);
}
}

Then set the XmlResolver as:

xdXhtmlContent.XmlResolver = new FileSystemDTDUriResolver();

One thing to note about this approach is that you cannot use a relative Uri with the XmlResolver, so you can either specify a file system path (using file:///) or (if you modify the sample code slightly) an absolute local URL, e.g. http://localhost/w3xml/DTD/

When Conditional Formatting Simply Won’t Do

corrywht — Wed, 19 Mar 2008 17:36:57 +0000

Excel has many neat features, Conditional Formatting being one of them. But one particularly irritating feature of Conditional Formatting is that you can only cater for a maximum of three possible states.

So, what do you do if, for example, you have a list of five possible strings that the user can enter, and you want to apply visual styles for each of the different strings? Well, you’ll need to roll up your sleeves and get stuck into VBA. Fortunately, it really is quite straightforward.

Conceptually, what you want to do is handle the ‘Change’ event on the active Worksheet – when the user changes a value, you want a piece of code to be executed. Here’s how:

Open up the VBA editor for the Excel workbook using Alt+F11 (or go to Tools > Macro > Visual Basic Editor)
In the Project explore, under VBA Project ([Workbook Name]) > Microsoft Excel Objects, open the worksheet object for the relevant worksheet by doubling-clicking (or right-clicking and selecting View Code)
Paste in the following code and change to suit your needs
You can test the code by returning to the Excel workbook

Private Sub Worksheet_Change(ByVal Target As Range)
   'Test that the Target is within the range of columns
   If Target.Column >= 2 And Target.Column <= 11 Then
        'Test that the Target row is correct
       If Target.Row = 15 Then
           'Handle the N/A case
           If Target.Value = "Not Applicable" Then
                Target.Font.Bold = False
                Target.Interior.Color = ColorConstants.vbWhite
           'Handle the Normal case
           ElseIf Target.Value = "Normal" Then
                Target.Font.Bold = False
                Target.Interior.Color = ColorConstants.vbGreen
           'Handle the Warning case
           ElseIf Target.Value = "Warning" Then
                Target.Font.Bold = True
                Target.Interior.Color = ColorConstants.vbYellow
           'Handle the Alert case
           ElseIf Target.Value = "Alert" Then
                Target.Font.Bold = True
                Target.Interior.Color = ColorConstants.vbRed
           ElseIf Target.Value = "Excellent" Then
                Target.Font.Bold = True
                Target.Interior.Color = ColorConstants.vbBlue
           'User has input an invalid string
           Else
                'Declare a response variable
               Dim Response
               'Show a message box
               Response = MsgBox("You must enter a valid status.", vbOKOnly, "Status Error")
           End If
        End If
    End If
End Sub

Et vóila! Share and enjoy.

Note: These instructions and the associated code are provided ‘as-is’, with no warranty, implied or otherwise, and is used at the reader’s own risk.

How to Print .PRN Files

corrywht — Wed, 19 Dec 2007 17:35:20 +0000

Ever been caught short without a printer to print off, say, an online order or a receipt for an online banking transaction? I know it has happened to me numerous times, but I was always reticent to use the “Print to file” option on the print dialog, because it used to be a pain to get the resulting .prn files to print (particularly when using network printers).

Luckily, I stumbled across this very neat PrnPrint utility, which, as the name suggests, prints a .prn file for you. The only caveat is that you must select the printer you wish to eventually print to in the Print dialog, as .prn files are formatted uniquely based on the target printer driver.

Enjoy!

Day Four in the Vista House…

corrywht — Thu, 26 Jul 2007 22:41:35 +0000

Eleven-oh-four AM and my newly purchased, supposedly “Windows Vista Ready”, Targus USB Bluetooth 2.0 EDR adapter broke my brand new Dell Latitude D630.

Everything seemed to be going so well initially, albeit with a handful of warnings from Windows encouraging me not to install third-party unsigned drivers: The installer worked fine, I got a nice Bluetooth configuration wizard at the end and was able to successfully pair and synchronise with my shiny Nokia 6300. Then things started to go awry. First, the mobile phone reported that the Bluetooth connection had failed. I was unable to re-establish the connection from the Bluetooth configuration applet, so I thought a restart might be in order.

That’s when things got really interesting. On restart, the boot loader screen appeared for a few seconds, then the screen went blank. The hard drive was active for maybe 30 seconds, then nothing; a black screen, no disk activity – this was looking bad. A hard reboot later, and things were not looking any better.

In the end, I had to remove the Bluetooth adapter, boot into Safe Mode and remove the Widcomm / Broadcom drivers. I felt like I had really dodged a bullet (and an embarrassing explanation to the Systems group). However, I wasn’t quite convinced that the adapter wouldn’t work, so I downloaded the latest Vista drivers from the Targus website. Running the installer, things were apparently much more positive, with no warnings from Windows about unsafe drivers, and I was once again able to pair with the mobile phone. Unfortunately, this wasn’t the end of my woes: Whilst the mobile phone was paired with the laptop, the Bluetooth stack was reporting to Nokia PC Suite that the phone wasn’t connected; try as I might, I couldn’t rectify the problem.

Exasperated, and more than a little concerned that I’d broken my four-day old laptop, I decided to bite the bullet and run System Restore. In the past (i.e. in Windows XP), this would have been more than a little foolhardy – I can say from experience that using System Restore in XP would be likely to destroy your PC, having had to format and re-install after running it – but I’d heard good things about its Vista successor. Luckily, my faith was rewarded with a system restored to its 11:03:59 state, with no evidence in the registry of any of the subsequent driver installs (based on a search for the strings “Widcomm” and “Broadcom”). This is certainly a good thing, given that so many drivers seem to dislike Vista and vice versa.

So, initial thoughts on Vista? It’s very shiny for certain, but seems more than a little wobbly at times – the Smart Card service keeps hanging on start-up; the Print Spooler service crashes every time I try to connect to a new printer and the OS keeps resetting my monitor setup every time I shut down or even log off – this is particularly annoying given that my desktop monitor is on the left, my laptop is on the right, and the Vista default is the opposite. I also dislike that you have to click the tiny little arrow beside folder names in Explorer to expand them, rather than having this as the default action when clicking a folder name in the tree, as in XP (although, as an aside, I think I may be very much in the minority using the full Explorer tree view interface so much – even other developers seem to be in a habit of double-clicking on My Computer, or worse, right-clicking the Start button… yak!).

More Vista experiences later!

On the subject of procrastination

corrywht — Wed, 27 Sep 2006 16:01:52 +0000

As I take my first tenative steps into the world of ~~self-publicism~~ sharing my deep and meaningful thoughts on everything, I have to wonder: What about the remaining two and bit chapters of my thesis?

Therein lies the rub: I have managed to find fourty-five minutes to set up a blog, read several others to get some style tips, and even choose a striking theme (speaking of which, is it dark and forboding in here or is it just me?), rather than make some dent in the remaining 5000 words.

Oh well. I’m sure some dust bunnies will be put out of their misery as soon as I have to write something more here…

In the meantime, may I politely suggest you dabble in MalContent?