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Brokenwire.NET::programming

Run ClickOnce app on startup
· 2009-08-26 14:07 by Thijs Kroesbergen for Brokenwire.NET

While toying with a small ClickOnce application I found out that there wasn’t an easy way to launch the app automatically on Windows startup. Of course I wasn’t the first one to have this problem so I started reading Ben Griswold aka Johnny Coder’s blog post on this topic. He sums up the pros and cons of several solutions nicely. (So go read that now, I’ll wait here.)

After trying out some of his suggestions I came up with the following plan:

I’ll put a shortcut in the Startup folder of the start menu. This shortcut will point to the executable file of my application, but it will start it with an additional parameter (“-L”). When the application detects that it is being run with this parameter it doesn’t show any of its forms, but just starts the .appref-ms shortcut that is already in the start menu. This shortcut will then start the application just as if the user him/herself clicked it.

The good thing about this solution is that this also fools Vista in starting a ClickOnce app on startup (so it WORKS!).

Why is this the best solution?

One small drawback: if the application is uninstalled then the shortcut in the startup folder will be left behind…

Code, show me code! Okay, so here is the code:

To install the shortcut in the startup folder of the start menu I’ve written this Install method. The ShellLink class is a wrapper around the windows API to make a shortcut. The corresponding article about creating and modifying shortcuts using C# can be found on vbaccelerator.com.

public static void Install()
{
  ShellLink shortcut = new ShellLink();
  shortcut.Target = Application.ExecutablePath;
  shortcut.Arguments = "-l";
  shortcut.WorkingDirectory = Path.GetDirectoryName(Application.ExecutablePath);
  shortcut.Description = "Start TestApp";
  shortcut.DisplayMode = ShellLink.LinkDisplayMode.edmMinimized;
  shortcut.Save(shortcutFileName);
}

Then to have the application launch itself, I've modified the Main method in Program.cs:

/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main(string[] args)
{
  if (args.Contains("-L"))
  {
    AppLauncher.Launch();
  }
  else
  {
    Application.EnableVisualStyles();
    Application.SetCompatibleTextRenderingDefault(false);
    Application.Run(new TestForm());
  }
}

The “Launch” method that finds the shortcut for the ClickOnce application and starts it via Process.Start. The determination of the location of the .appref-ms file can be a bit tricky, this code works for me but your mileage may vary.

public static void Launch()
{
  string shortcutFileName = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Startup), "Start TestApp.lnk");
  string publisherName = Application.CompanyName;
  string productName = Application.ProductName;
  string allProgramsPath = Environment.GetFolderPath(Environment.SpecialFolder.Programs);
  string shortcutPath = Path.Combine(allProgramsPath, publisherName);
  shortcutPath = Path.Combine(shortcutPath, productName) + ".appref-ms";
  System.Diagnostics.Process.Start(shortcutPath);
}

You can try it out for yourself with this small sample:

ClickOnceStartupTestApp.zip which is also published here: http://www.brokenwire.net/~thijs/clickoncestartup/publish.htm

Have fun!

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The madness of “exclusive” row locks
· 2009-06-24 15:19 by Thijs Kroesbergen for Brokenwire.NET

Yesterday I discovered some really weird behavior of SQL Server. I had a case where I could read a record that was exclusively locked by someone else. Considering the word “exclusive” you would expect that when one transaction has an exclusive rowlock an other transaction would be unable to read that same row. But there is one specific case where this isn’t true. In that case it is possible to read a record that is locked exclusively by someone else.

It took me (together with a colleague) a lot of time to finally find out what was happening.

To reproduce this behavior you need a test-table with some random data in it.

CREATE TABLE [MyTable]
 ([Col1] bigint PRIMARY KEY CLUSTERED, [Col2] bigint)
INSERT INTO [MyTable] ([Col1], [Col2]) VALUES (1,10)
INSERT INTO [MyTable] ([Col1], [Col2]) VALUES (2,20)
INSERT INTO [MyTable] ([Col1], [Col2]) VALUES (3,30)
INSERT INTO [MyTable] ([Col1], [Col2]) VALUES (4,40)
INSERT INTO [MyTable] ([Col1], [Col2]) VALUES (5,50)

You can put this table in any database, as long as it doesn’t have snapshot isolation turned on. The recovery model for your database doesn’t matter.

Now let’s run some queries and see what happens. To be able to test this properly you should run two different session against this table. To be able to hold (and see) the locks that used you need to start a transaction and run some statements, but don’t complete the transaction (yet).

First in the first window of the Query Analyzer (which I’ll refer to as session 1) select one row from the table and request an exclusive rowlock on it with the XLOCK and ROWLOCK table hints.

session 1:

SET TRANSACTION ISOLATION LEVEL READ COMMITTED
BEGIN TRAN
SELECT Col1 FROM [MyTable] WITH (XLOCK, ROWLOCK) WHERE [Col1] = 3

To verify the locks that where put into place you can run sp_locks to check the locks that are granted to the connection (spid) that you used to perform the actions for session 1.

spid   dbid   ObjId       IndId  Type Resource                         Mode     Status
------ ------ ----------- ------ ---- -------------------------------- -------- ------
56     21     69575286    1      PAG  1:41                             IX       GRANT
56     21     69575286    1      KEY  (030075275214)                   X        GRANT
56     21     69575286    0      TAB                                   IX       GRANT

As you can see there is an “X” (exclusive) lock on the first key of this table. (The other locks are “IX” (intentional)). Now let’s move to session 2 and see if we can we retrieve that record.

session 2:

SET TRANSACTION ISOLATION LEVEL READ COMMITTED
BEGIN TRAN
SELECT Col1 FROM [MyTable] WHERE [Col1] = 3

I did expected this statement to just “hang” while waiting for the record to come available. But I was surprised to see that the record could be retrieved without a problem. Also, sp_locks doesn’t show any additional locks for this statement, not even a shared lock!

If you rollback session 2 (to clear everything that might have happened) and retry it with the HOLDLOCK table hint you do get the expected behavior, because the select in session 2 now will wait for the transaction in session 1 to complete.

To understand what is happening here you should remember one of the rules of read committed data access. This rule says that you can read any row as long as it’s in a committed state. The row we’re trying to read here is in a “clean” state (it’s not marked “dirty” by the system). In this case the optimizer decides that it doesn’t hurt to retrieve it via the index without checking for locks. So your table doesn’t even need a primary key, a long as you have an index containing the requested data the rowlocks may be skipped at will.

So if the locked record has not changed and the data for requested columns is stored in an index and you are working from an READ COMMITTED isolation level then the exclusive lock is possibly not honored.

One possible workaround is to add a “HOLDLOCK” table hint to the select in session 2. Alternatively you can actually update the record to have it exclusively locked (and marked “dirty”) in session 1. The last possibility is to lock an entire page instead of just one row by using the PAGLOCK hint. Exclusive page locks do prevent all other readers for the rows in that page.

There’s a thread on http://social.msdn.microsoft.com/ posted by someone who has observed the same weird locking behavior. A Microsoft employee responded with:

Using XLOCK in SELECT statements will not prevent reads from happening. This is because SQL Server has a special optimization under read committed isolation level that checks if the row is dirty or not and ignores the xlock if the row has not changed. Since this is acceptable under the read committed isolation level semantics it is by design.

Perhaps the worst thing about all this is that this behavior cannot be found easily in the Books Online. A small note somewhere in the section about table hints would have be nice. There are some hints in KB324417 (which applies to Sql Server 2000). Combine all that with the fact that the optimizer may choose to do this at will, you’ll have a very hard to find bug in your sql code.

Conclusion:

It took me a lot of time to find out what was going on here. So remember kids: a SELECT with XLOCK and ROWLOCK hints doesn’t mean that you are the only one who can read those rows!

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Pimp my software
· 2009-06-23 09:00 by Thijs Kroesbergen for Brokenwire.NET

Everyone who has done some (serious?) software development knows that we have several different methods to run our project. We also know that not all methods are equally successful. But one of our favorite things to do is compare our ways of doing things with others in the more “traditional” trades.

So a little while ago I was watching MTV’s "Pimp My Ride", and then I was thinking, what would software development look like if we did it the “Pimp My Ride” way?

So let’s see what that would look like. For those of you who don’t know the Pimp My Ride TV show, it goes like this:

The show starts by showing a teenager with a banged up car. That car gets picked up by the shows host and brought to a garage. Then a team of mechanics goes wild on the car by remodeling it completely. Then the owner is brought in, the car is presented and a happy guy (or girl) leaves the shop with a new ride. If you want to see this for yourself, take a look at the MTV website.

Now let’s break that down into the parties involved. The core group of people involved is of course the team of mechanics. This team designs and builds the car. The way this team is composed is that several people with different specialties are brought together in the right mix. In our world this would be team of highly skilled software engineers. This way each member should have its own specialty like data-access, user interfaces and such. Perhaps the most important thing to notice is that all team members are involved from start to finish.

Then there’s the host of the show, he gets to pick up the car, monitor the work on it and deliver it back to the owner. In the software development world this could be the project manager with a bit of help from some sales guy perhaps.

Last but not least we have the owner of the crappy car. This is comparable our customer, who has a problem (a crappy car, or some complex business process) and needs someone to solve it for him.

That wraps up the parties involved, now lets move to the process.

At the start of each episode (project) the old car gets picked up from some lucky bastard by the presenter of the show, a rapper known as “Xzibit”. They chat a bit and X gets a pretty good idea about the likes and dislikes of the car’s owner. This translates to an combination of sales and analysis. There’s communication with the customer, and both the scope and the requirements are set. For example, the owner drives a VW Beetle (scope) and likes to sing (requirement).

Once this is done the car is brought back to the garage and the whole team gets to take a good look at it. Then they sit together and each specialist tells what he thinks that needs to be done to the car.

Lets see how that meeting works out…

Paint specialist:

“I’m gonna put on a base layer of toxic green paint, and then I’ll airbrush some hot flames on the side of this wicked car!”

User Interface guy:

“I’m going to design a WPF based interface with nice glowing buttons which animate on mouse-over”

Engine tuner:

“Let’s upgrade the engine so it can do 0-60mph in 2.9 seconds! For that I’ll use this nice turbocharger kit.”

Database guru:

“I recommend that we store our data in a clustered SQL Server database, and we’ll use LINQ for our data access layer. This way we will have performance and speedy development all at once!”

You get the point ;). This meeting is like the project kickoff. Here the architecture is determined and the individual components are defined.

Then they get to work. Each specialist does what he does best, and they work together as the gears of a well oiled machine. Sometimes they encounter something unexpected, but with all the knowledge they have on board they will continue to deliver the finished product right on schedule. This is actually exactly the same thing that is (or should be) happening in any software delivery process.

Finally during the last minutes before the car’s owner arrives the finishing touches, such as polishing the car, are applied. Then the big unveiling takes place, and a happy customer leaves the building.

“You’ve officially been pimped”

The handover of the car’s keys translates to the delivery phase in our world. This where the happy customer accepts the finished product. And a happy customer is what we are aiming for!

To conclude this rant, lets see why this “Pimp My Ride” process should work for software as well:

But of course there are some differences as well, so why doesn’t this work for software?

It looks like this comparison doesn’t hold up too well (but I had fun trying it anyway). I do think that we like to over-complicate things because with software it’s so easy to create anything our mind can come up with. And because of our human nature we just love to try stuff that hasn’t been done before. Perhaps, given some more time and thought, the expectations for software will become just as clear as the expectations we have of a car.

So what do you think? Does any of this make sense? Is building software harder then building a custom car? Are we spoiled by all the options we have and do we over-complicate?

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Quick Visual Studio Tip
· 2009-04-19 14:07 by Thijs Kroesbergen for Brokenwire.NET

Press CTRL + SHIFT + V to cycle through previous clipboard entries (and paste them). This way you can “cut” several pieces of code, and “paste” them somewhere else without going back and forth. (You could also use “copy” multiple times and then use this to “paste” that, but of course nobody is interested in copying code…)

There are more hotkeys in Visual Studio that are not so well known, take a look here.

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Decrypting Sql 2005 SPs made easy
· 2009-03-25 15:05 by Thijs Kroesbergen for Brokenwire.NET

Today I ran across a problem where I desperately needed to peek inside a stored procedure used by Team Foundation Server. The only trouble was that the stored procedure was created with the “WITH ENCRYPTION” clause appended, so I couldn’t see the source.

To decrypt the stored procedure I used a stored procedure called dbo.sp_SpDeObfuscation, which can be found here and/or downloaded here.

Please keep in mind that you need to run the SP from an DAC (Dedicated Admin Connection)

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Use VPC fullscreen on your large screen
· 2009-02-27 13:35 by Thijs Kroesbergen for Brokenwire.NET

I haven’t tried this for myself yet, but as you can read in the description hotfix number 958162 will let you use VPC 2007 SP1 full-screen on your large kick-ass monitor. The maximum resolution for a virtual machine now is 2048x1920 instead of the old 1600x1200. This feature has been on high demand for ages!

Besides the maximum resolution several performance and stability fixes have been made in the virtual machine networking.

To install this hotfix you’ll need to run msiexec.exe  from an elevated command prompt. Just double click won’t work.

To install this update, save the .msp file locally. If you are running Windows Vista, Windows Vista Service Pack 1, or Windows Server 2008, run the update from an elevated command prompt. To do this, use the following command syntax:

msiexec /p path of .msp file

If you are running an earlier version of Windows, double-click the downloaded .msp file to start the installation process. Then, follow the installation instructions.

Direct download links:

32 bits
64 bits

Via [Joy of Setup]

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