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behaug@gmail.com (Bjorn Erik Haug) — Tue, 15 May 2007 09:15:14 GMT

WTF!? What am I supposed to do when I have to unlock, but the inputs are disabled?

Windows Forms UserControls in IE

behaug@gmail.com (Bjorn Erik Haug) — Fri, 20 Apr 2007 22:47:05 GMT

I've been working on using Windows Forms UserControls hosted inside of IE. It's easy to get started, but there's very little good information to be found on the details of this out there. Especially for running them in an intranet where you don't want to configure the security settings on every client machine. Here are some of the things I've figured out while making this work.

I won't go into the basics. You can easily find this information on Google. Try this one for instance. Also, if what you need is pretty graphics and not application logic, consider using Flash or Silverlight instead.

I was trying to get my usercontrol to play under the restricted Intranet Zone. This is the Zone that IE uses when there are no dots in the domain name, like localhost or a local intranet server name. It's only slightly more permissive than the Internet Zone, and it's still giving a lot of issues.

Allow partially trusted callers

To make the control at all load in the browser in the Local Intranet Zone, the assembly and all references assemblies need to allow partially trusted callers. To enable this, put [assembly: System.Security.AllowPartiallyTrustedCallers] in the AssemblyInfo.cs file of the class library containing the control. You can't reference assemblies that don't have this tag, or your control won't load. Also, be sure you don't call any methods that require more trust than the Local Intranet Zone provides, or you'll get an exception.

Troubleshooting

Try Full Trust

If you are having trouble getting your control to display, try and set the LocalIntranet Zone to run with FullTrust permissions. This is done in the Control Panel > Administrative Tools > .Net Framework 2.0 Configuration tool (assuming NetFx 2.0). Navigate to the My Computer > Runtime Security Policy > Machine > Code Groups > All_Code > LocalIntranet_Zone node. Right click it and go to Properties. Under the Permission Set tab, change the dropdown from LocalIntranet to FullTrust, and click OK.

Now everything running from http://localhost and any other hostname with no dots in it will have permission to format your harddrive. But just make sure your UserControl doesn't do anything malicious and you'll be ok. If your control works now, the problem was security. If it still doesn't then it's possibly a loading error, or an exception in your code.

Logging

Internet Explorer gives very little indication on the web page to what may be wrong. But there is a way to have it log what it's doing when trying to load and instantiate your control. This logging is enabled in the registry. This can tell you whether the DLL wasn't found, or of there was an exception when instantiating it. You can also monitor the assembly loading with the Assembly Binding Log Viewer. Open this by starting the Visual Studio 2005 Command Prompt and typing fuslogvw.

Also you can take a look at the IIS logfiles for the website you are running the control in to see if the DLLs are getting downloaded. HTTP code 200 means OK, and 304 means it was taken from cache.

Avoid the Bin directory

Remember that the bin directory on an ASP.NET website does not allow retrieving DLL files. So don't put your control in there. This rules out adding a Copy Local reference to the control's project to have it copied automatically. Rather set up an xcopy command in the Post-build events of the control's project that copies the compiled files to the web project.

Clear Download Cache

The .Net Framework will cache the downloaded assemblies in the Download Cache. Under development this can sometimes cause some problems with the DLL not getting updated. This cache can be cleared with the gacutil utility by issuing the command gacutil /cdl. I recommend adding this as a build action on the project containing the control. Go to properties on the project in Visual Studio and in the Build Events tab put this line in the "Post-build events command line" box: C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\gacutil.exe /cdl. Now the cache will be cleared each time you build a new DLL. Just note that the browser needs to be closed when you clear the cache, or it will hold a lock on the DLL and the clear will fail.

Use IIS, not the VS built-in web server

I've had some strange caching issues when running from the built-in web server in Visual Studio. Switching to using IIS instead made everything work much better. Open the properties on the web project in Visual Studio, and under the Web tab choose to Use IIS Web Server, and click the Create Virtual Directory button.

Attach the debugger

You can attach the debugger to IE and be able to debug the control. But you will have to manually attach to IE after you have loaded the page. If VS is set ut to attach to IE when you start the project, it will not get attached to the managed host within IE, and you will not be able to debug.

This means you won't be able to debug the initalization of your control.

Separate assembly baseclass

One more thing to notice: Your control will not work if you inherit from a baseclass in a different assembly, even though that baseclass inherits from UserControl. I guess the IEHost will check for inheritance on UserControl before it loads the dependent assembly. If you need all your controls to be castable to some common type, or to expose the same methods and properties, consider having them all implement a common interface.

JavaScript

COM visible

You control can interact with JavaScript in the page. The public properties and methods on your control are usable from javascript. Just have the script get a reference to the object tag and then just call the methods and properties by name (only simple types like string, int and double works though). But before javascript can access your methods and properties you need to make your control COM visible. This is done in the AssemblyInfo.cs file by adding (or changing) this attribute: [assembly: ComVisible(true)]. By default this is set to false, but needs to be true.

Polling instead of events

UserControls are also able to fire events that can be handled in javascript. But this requires Managed Code permissions, which is not available in the Local Intranet Zone. So events won't work. If you need your javascript to know when something happens in your control without using events, you can make your control expose a property that indicates event state, and then have a javascript timer poll on that property. This isn't as nice as real events, but does the job.

Issues

Resizing is blocked

A strange issue with the Local Intranet Zone permissions is that resize events to the control are blocked. If you set your object tag to, say, 100% width and height, the control will be sized as expected when the page loads. But if you then resize the browser window, the control's content will not resize, and it will be clipped. Resizing works as it should with Full Trust.

One way I've found to work around this strange quirk is to expose a SetSize(with, height) method on my control and have javascript in the page set the correct size on the document.onresize event. With some clever scripting I got this right.

Activation

Since the control is an embedded object, it is subject to the Click-To-Activate behaviour of Internet Explorer. This shouldn't be news to you. But the issue is that the control behaves really badly when it's not activated. It's slow to paint when you scroll the page and has all kinds of issues if you try to emulate paging with showing and hiding them. Once they are activated they work quite well. So if you experience problems, make sure the controls are activated before you decide that this technology is broken.

WCF

If your control is calling back to the server using a web service, do not implement this using WCF in the control. The System.ServiceModel assembly do not have the AllowPartiallyTrustedCallers attribute, and will cause your control not to load under Local Intranet Zone if you reference it. Rather use normal web services.

Please let me know if anything I've said here is wrong or inaccurate, or if there are some other issues I should know about. There is far too little info out there on these things. And what is there is hard to find because of the obvious searchability issue between web forms usercontrols and windows forms usercontrols.

Villavent

behaug@gmail.com (Bjorn Erik Haug) — Tue, 30 Jan 2007 14:20:38 GMT

We've got a Villavent at home. And it's quite practical, sort of. It's this ventilation system throughout the house that keeps the air fresh and transports odors out of the bathroom when someone has gone about their own business, and ventilates the moist air out from the shower so it doesn't go into the walls and ceiling and make it rot and grow little brown spots.

It's all controlled from one central location; a knob on the kitchen fan above the stove. Turn it left and its a regular kitchen fan, turn it right and it starts sucking air from the pipes going to the bathroom and shower.

It's just great. In theory, that is.

In practice, I wake up in the morning all groggy and barely alive, stumbling out of bed and finding my way to the shower on auto pilot while rubbing my eyes with the back of my hands. At that point it's not so great that it order to not ruin the walls and ceiling and have them grow brown spots I have to first go upstairs to the kitchen and fiddle with knobs. For some reason it just doesn't get done. Somehow the bathroom is just not getting ventilated. And somehow brown spots have appeared.

It's my own fault, I know. - Stupid Villavent.

Taming the Tab key's little brother

behaug@gmail.com (Bjorn Erik Haug) — Tue, 19 Dec 2006 12:16:59 GMT

I use the Tab key all the time. From navigating between input fields in applications to indenting my code. But sometimes when I press it it doesn't work. Instead I just start getting everything I type in capital letters.

That's the Tab keys little brother. His evil little brother whose only purpose in life seems to be to get in my way and annoy me. Why would I want to enable a permanent inversion of the capitalization of everything I type? I wouldn't. It's as useful as a "13375p34k" key that changes everything to geekish. It's of no practical use. If I want to write in all caps to yell at some bonehead in a forum I'll keep the shift key down. Or I'll select the text I wrote normally (but with a lot of aggrevation and hostility) and run the "Make Uppercase" command in my editor.

So I don't want it anymore. I could physically rip the key off of the keyboard, but I don't want go to that extreme. So that's why I hit google and found this way to just relieve it from its duty.

There's a registry key that lets you remap keyboard scan codes to other codes. So all you need to do is map the scancode of the caps lock key to something else, and the beast is tamed. I ended up choosing to map it to work just like a second Tab key. So when I miss the real Tab, its little brother is there to help instead of mess things up.

I created a .reg file that contains this:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
"Scancode Map"=hex:00,00,00,00,00,00,00,00,02,00,00,00,0f,00,3a,00,00,00,00,00

Once you change this in the registry you will need to reboot before it takes effect.

If you want more details and a list of possible scan codes check out this page.

Combine() only two paths?

behaug@gmail.com (Bjorn Erik Haug) — Mon, 18 Dec 2006 13:42:56 GMT

How come the System.IO.Path.Combine() method takes only two parameters?

Doesn't it makes a lot more sense to take (params string[] paths) instead of (string path1, string path2)? So that instead of

Path.Combine(Path.Combine(rootPath, subFolder), "filename.txt")

it's just

Path.Combine(rootPath, subFolder, "filename.txt").

Seems so obvious, I can't believe they made it like that for no reason. So what's the reason?

Bathwater resistant

behaug@gmail.com (Bjorn Erik Haug) — Thu, 23 Nov 2006 13:42:42 GMT

- Nooo!

That was what startled me from my TV viewing. It was coming from my wife in the bathroom where our oneyearold had just run in. I thought no more of it. It's not like that's really unusual.

- Shit! Ohhh! My Goood!

Ok. This was beginning to sound like a bit more than nothing. What's the matter, I asked.

- Shit! Your cellphone! He dropped it...

Oh..

- Into the bathwater!

OH! Crap! I ran in there. She had already picked it up and was drying it off with a towel. And my son was just standing there watching the action like he was getting the answer to his question: "I wonder what happens if...". I was ready to throw the baby out with the bathwater, literally.

Luckily, the phone made it. It was completely soaked in soapwater and baby oil, but after drying it properly in front of the air conditioner it's been working just fine.

Refactorings

behaug@gmail.com (Bjorn Erik Haug) — Wed, 15 Nov 2006 20:28:31 GMT

The excellent developer and my former schoolmate Bent André Solheim just posted this great blogpost about two of my favorite refactoring techniques: Guard Clauses and Composed Methods. This is stuff that I can really recommend using. I've been using these techniques for a while and they really do make your code easy to read and maintain, and it has less bugs because of it.

I think the refactoring I use the most when working on legacy code is Rename. Proper naming of variables, methods and classes are the number one most important readability aid. Having lots of needless hungarian notation, abbreviations, or names that just mean nothing, adds noise and obfuscation.

Second must be grouping together related blocks of logic within long methods and then using Extract Method to work towards Composed Methods. I often end up restructuring a lot before I can extract the methods because the code is tangled up in itself, like reuse of local variables (please, don't do that, and don't declare everything at the top of the method).

Then it's reducing the levels of nesting by using Guard Clauses. And extracting methods often go hand in hand with this. If you have an if-statement and then a block of code after it that is to be executed regardless, then you can't make a guard that returns early from that method.

public void DoWork(string a, string b)
{
    // Handle the DoStuff first
    if (a != null && b != null)
    {
        if (a.StartsWith(b))
        {
           DoStuff(a, b);
        }
    }

    DoImportantThing();
}

This if-statement can't be made a gaurd clause like it stands. But extracting that block to a method of its own cleans that up:

public void DoWork(string a, string b)
{
    HandleStuff(a, b);
    DoImportantThing();
}

private void HandleStuff(string a, string b)
{
    if (a == null || b == null)
       return;

    if (!a.StartsWith(b))
       return;

    DoStuff(a, b);
}

Debugger.Launch()

behaug@gmail.com (Bjorn Erik Haug) — Fri, 03 Nov 2006 13:43:47 GMT

Have you ever wanted to debug some .Net code that you have running in some other process that you just can't get into? I recently had the problem with Custom Actions in a Windows Installer. The custom action is a .Net Installer class that I wanted to debug. But I couldn't just attach the debugger to the running msiexec instance. It wouldn't hit my breakpoints.

This is where the System.Diagnostics.Debugger class comes in real handy. It's got a method called Launch() that will tell Windows to open a debugger. You get this dialog box asking you if you want to debug the code, and what debugger to attach:

If you have Visual Studio up and running you can attach it. The debugger stops right at the Attach() method call just like if it was a breakpoint.

By the way, as a sidenote to the custom actions, the custom action argument name that holds the virtual directory name in a Web Setup installer is [TARGETVDIR]. Took me some googling about to figure that out. Good info here.

Microformats

behaug@gmail.com (Bjorn Erik Haug) — Fri, 29 Sep 2006 22:15:09 GMT

I've often been thinking that, since HTML is a markup language that is marking the content with semantic meaning -- like, that some text is a <p>paragraph</p> or a <h1>headline</h1> -- that other types of semantic meaning should also be possible to mark up. but the set of tags available in HTML is quite limited.

If, say, NNUG is publishing info on the next session that's scheduled for thursday in two weeks at HiA (the local college), they should be able to tag that date as a <date> and the location as a <location>. Like this:

Next NNUG session will be on
<date utc="2006-10-12T17:15:00+01:00">thursday in two weeks</date>
at <location>HiA</location>.

This way my browser would be able to understand the date and perhaps show me a tooltip where it has translated it into my local timezone and display format. And it would be able to add that information to my calendar application just like a vCalendar file, and I would be notified half an hour before so I could actually get there on time and not come tip-toeing in in the middle of the session and wonder why they're not using the frikkin projector. (Not that I use to be coming in late, I'm just making this up for effect, and they already have a .vcs file download for this).

Well, it turns out this is already possible. Not by introducing new tags like that, because that's just silly, and your strict xhtml wouldn't validate anymore. (You could ignore that and go back to html 4, but then height=100% would be working like it should, and we can't have that, can we?). But rather by allowing you to assign semantic meaning to existing tags. This is what they're calling microformats. So with this, that NNUG session info can be read as a vCalendar entry by the browser. To make it work you just add some span, div, abbr or whatever tags you like around the specific fields, and then use classes on them to indicate the field types. Quite elegant, really. So now that session info can be written like this:

<span class="vevent">
   <span class="description">Next NNUG session</span>
   will be on <abbr class="dtstart" title="2006-10-12T17:15:00+01:00">thursday in two weeks</span>
   at <span class="location">HiA</span>.
</span>

With some plugin in your browser you can have it detect these microformats, and already a long list of services are supporting them.

If you want to style this with additional CSS classes, just list more than one class name in there separated by space. The only aber that I can see straight away is if you've already been using those class names for CSS styles, and now that description field looks really odd all of a sudden. Or you find you've got broken, unintended microformat definitions in your markup by accident. Plus the fact that everyone that's reading your fancy microformatted website needs to go and download that plugin before they get any use from it. But that'll change, soon, hopefully.

Automated home

behaug@gmail.com (Bjorn Erik Haug) — Fri, 29 Sep 2006 19:27:22 GMT

My friend Sondre is dreaming of automating his house. Having his basement filled with racks of servers and having sensors all over the place. He wants voice recognition to help him turn the lights on and off and control his music. His music will follow him from room to room by routing it to that room's set of integrated sound system, and doors will open as he approaches.

That's kinda cool. But really, if I was to spend a lot of money automating my house I'd want it to help me with the stuff I don't mind doing myself. I just don't think its too much hassle opening the door when leaving the room, or turning the lights on. And I actually enjoy putting on music manually. But if I could have my house clean itself, though, that would be another thing alltogether. Now we're talking actual value.

If it would constantly keep the toilets shining and pleasantly fragrant, the floors swept and toys out of harms way, keep stains off my rug, ants out of my kitchen, the waste basket empty, the lawn mowed, the fridge emptied of dated goods, the car washed, my bills paid, my inbox free from spam, and dinner ready on time. Then I'd start doing the mortgage-math.

"Computer! Lights on!", my ass.

"Bjorn, your car is washed now. Would you like it waxed as well?" - That's more like it!

Projector trouble

behaug@gmail.com (Bjorn Erik Haug) — Fri, 29 Sep 2006 18:50:00 GMT

I addended the local .Net Users Group the other day. It was a good session. Mostly for the social aspect as always, but the sessions were also quite interesting.

But there was this one thing that got most of my attention: How many .Net experts does it take to get a projector working? There were two sessions; one mostly about fiddling with scrollbars on a too-low resolution projector, and one which turned out to be a live podcast with no picture at all.

I guess that projector didn't like be used for non-Microsoft stuff, because that last session was about Mono. Luckily he was a good speaker so it turned out interesting anyway.

(Does this say more about people, laptops or projectors? Seems to me this is always a problem. Why can't these things just work?)

Web project refactoring

behaug@gmail.com (Bjorn Erik Haug) — Thu, 14 Sep 2006 14:49:56 GMT

Refactoring in Visual Studio 2005 with Web projects is incredibly slow. This helps alot!