The Ramblings of Rob Cooper: Software Development

Finally The Truth About "using" and Dispose()

Tue, 22 Apr 2008 09:51:26 GMT

The Problem

During the good chat with some fellow students last night, the top of whether or not "using" should be used over an explicit Dispose() method call when using objects like Graphics came up.

Now, this one has been bugging me for some time, and I have never actually sat down to investigate it, so I thought I should. I have been told on several occasions that I should use "using", but when questioning why, I get no real answer that makes any sense. Seems like a classic "every knows the best practice but doesn't understand the practice or why its best" scenario!

So, I made some very small code samples, one using "using" the other using Dispose(). Here are the samples FYI:

"using" Code

   1: private void Form1_Load(object sender, EventArgs e)   2: {   3:     using (Graphics g = Graphics.FromHwnd(this.Handle))   4:     {   5:         MessageBox.Show("this is between the graphics instantiation and disposal");   6:     }   7: }

Dispose() Code

   1: private void Form1_Load(object sender, EventArgs e)   2: {   3:     Graphics g = Graphics.FromHwnd(this.Handle);   4:     MessageBox.Show("this is between the graphics instantiation and disposal");   5:     g.Dispose();   6: }

As you can see, nothing fancy! And here are the results (intermediate language - "IL") courtesy of ILDASM:

"using" IL

   1: .method private hidebysig instance void  Form1_Load(object sender,   2:                                                     class [mscorlib]System.EventArgs e) cil managed   3: {   4:   // Code size       36 (0x24)   5:   .maxstack  1   6:   .locals init ([0] class [System.Drawing]System.Drawing.Graphics g)   7:   IL_0000:  ldarg.0   8:   IL_0001:  call       instance native int [System.Windows.Forms]System.Windows.Forms.Control::get_Handle()   9:   IL_0006:  call       class [System.Drawing]System.Drawing.Graphics [System.Drawing]System.Drawing.Graphics::FromHwnd(native int)  10:   IL_000b:  stloc.0  11:   .try  12:   {  13:     IL_000c:  ldstr      "this is between the graphics instantiation and dis"  14:     + "posal"  15:     IL_0011:  call       valuetype [System.Windows.Forms]System.Windows.Forms.DialogResult [System.Windows.Forms]System.Windows.Forms.MessageBox::Show(string)  16:     IL_0016:  pop  17:     IL_0017:  leave.s    IL_0023  18:   }  // end .try  19:   finally  20:   {  21:     IL_0019:  ldloc.0  22:     IL_001a:  brfalse.s  IL_0022  23:     IL_001c:  ldloc.0  24:     IL_001d:  callvirt   instance void [mscorlib]System.IDisposable::Dispose()  25:     IL_0022:  endfinally  26:   }  // end handler  27:   IL_0023:  ret  28: } // end of method Form1::Form1_Load

Dispose() IL

   1: .method private hidebysig instance void  Form1_Load(object sender,   2:                                                     class [mscorlib]System.EventArgs e) cil managed   3: {   4:   // Code size       30 (0x1e)   5:   .maxstack  1   6:   .locals init ([0] class [System.Drawing]System.Drawing.Graphics g)   7:   IL_0000:  ldarg.0   8:   IL_0001:  call       instance native int [System.Windows.Forms]System.Windows.Forms.Control::get_Handle()   9:   IL_0006:  call       class [System.Drawing]System.Drawing.Graphics [System.Drawing]System.Drawing.Graphics::FromHwnd(native int)  10:   IL_000b:  stloc.0  11:   IL_000c:  ldstr      "this is between the graphics instantiation and dis"  12:   + "posal"  13:   IL_0011:  call       valuetype [System.Windows.Forms]System.Windows.Forms.DialogResult [System.Windows.Forms]System.Windows.Forms.MessageBox::Show(string)  14:   IL_0016:  pop  15:   IL_0017:  ldloc.0  16:   IL_0018:  callvirt   instance void [System.Drawing]System.Drawing.Graphics::Dispose()  17:   IL_001d:  ret  18: } // end of method Form1::Form1_Load

Conclusion

So, as you can see, the "using" method wraps the code inside the scope of the statement within a "try" block of a "try/finally", placing the Dispose() call in the finally, meaning it will always get executed even if an Exception is thrown. However, using the explicit Dispose() method, if an Exception is thrown, then it will not get disposed of, meaning it could be sat on the heap for a few milliseconds or even a few minutes, not good!

I guess this is why MSDN refers to the "using" statement as the "convenient syntax for correct use of IDisposable objects".

~~I believe the VB developers out there do not have an equivalent available, so make sure you are wrapping all of your disposable objects calls in try/finally blocks!~~

Update: I have been told that VB.NET 2.0 does actually have a "using" statement as well, which looks surprisingly like the C# syntax! http://msdn.microsoft.com/en-us/library/htd05whh.aspx

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Great Summary of New VS2008 Goodies

Thu, 07 Feb 2008 09:12:54 GMT

I came across a great summary page of the new features available to us geek's within the new Visual Studio 2008 release. Definitely worth a read, there were things on there I were not aware of that may be useful! (I TinyURL'd it since its quite a long address!) =)

http://tinyurl.com/2zhmpn

I hope they make you more productive!

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Excellent Video Tutorials from Beth Massi

Mon, 10 Sep 2007 20:49:53 GMT

Beth Massi has created two series of video tutorials on using forms over data. They contain lots of usable, and applicable tutorials. There is nothing worse than seeing a very well presented video/webcast that you walk away from thinking about how you like what you just saw, but how and why the hell would you ever need to incorporate it into any applications!

Here's links to Series 1 and Series 2 of the video series.

They have both helped, and continuing to help me a great deal in my studies, so Beth, I thank you!

Note: The videos are in VB.NET. But TBH, if you work in .NET, you will be able to get the idea of the code.

Visual Studio 2008 (Formerly "Orcas") Install Issues

Fri, 10 Aug 2007 10:07:11 GMT

Looks like there have been some other issues with the install of VS2008 Beta 2..

Aaron Stebner has posted some workarounds for those having issues that also use IIS.

I haven't had any of these problems myself, but it may be useful for others.

Visual Studio 2008 (Formerly "Orcas") Beta 2 Installation (Part 2)

Wed, 08 Aug 2007 10:23:06 GMT

Well, I finally managed to get the damn thing installed, but now I have two other problems!

I cannot create a VSTO project (any type of Office Code-behind or Add-In). I get a "write to protected memory" error.
I cannot create Silverlight projects. I get a "referenced component" error not found on all the referenced components.

Talk about when it rains, it pours!

Here's what I have done so far to try and remedy the issues (currently to no avail):

VSTO Project Creation

Here is the error message I am getting:

Removed VSTO from the system.
Reinstalled VSTO (following restart).
Ran a repair install, according to the setup, everything is fine.

At a bit of a loose end with this one, not quite sure what else to try!

Silverlight Project Creation

Here's the reference errors I get:

Warning    1    The referenced component 'system.Xml.core' could not be found.
Warning    2    The referenced component 'system.silverlight' could not be found.
Warning    3    The referenced component 'System.Core' could not be found.
Warning    4    The referenced component 'system' could not be found.
Warning    5    The referenced component 'mscorlib' could not be found.
Warning    6    The referenced component 'agclr' could not be found.

And here's what I have tried so far:

Removed the Silverlight VS plug-in from Visual Studio.
Removed the Silverlight Runtime from the machine.
Reinstalled the Runtime (following reboot).
Reinstalled the VS plug-in.
Created a new Silverlight Project.

And all the references were still appearing as "missing". So I checked the references list, and got the (expected) location of the DLL's. I browsed to the location in Explorer, and low and behold, the files are not there. So I then checked out the Silverlight directory in "C:\Program Files\Microsoft Silverlight" and the DLL's being referenced in the Visual Studio Project were all there!
So I then tried:

Copying the DLLs to the expected directory.
Manually referencing the files.

Of course, neither of these worked either!

I am now downloading the VPC Images to see if they work any better.. I will keep you updated!
If anyone has any ideas/comments/suggestions then let me know!

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Visual Studio 2008 (Formerly "Orcas") Beta 2 Installation

Tue, 07 Aug 2007 23:06:06 GMT

UPDATE: I NO LONGER HAVE THESE CAB FILES, I DELETED THEM AFTER ORCAS CAME OUT OF BETA.

DO NOT EMAIL ME ASKING FOR THEM!!

DOWNLOAD THE EXPRESS EDITION OR PAY FOR THE PRO VERSION!

Well, like most developers, I have been itching to have a chance to play with VS2008. There's been some pretty big developments both inside the IDE as well as outside (such as Silverlight) so there's lots of good stuff happening.

However, I ran into problems with the install. And it seems I am not alone.

I kept receiving a "1335" Error - Corrupt Cab Files. So I went ahead and downloaded the (3GB) Image again.
I received the same error. So then I am thinking "Damn, maybe the image is damaged" (although I was incredibly skeptical that MS would leave a damaged Image on one of the most popular downloads!). So I thought there's only one way to be sure, so I downloaded the Team System Image (I started with Pro). But sadly, same problem occurred.

So I figured, lets check the CAB files themselves, and see which ones are damaged. So I fired up WinRAR and ran a test on all the cab files in the image. I found I had one damaged CAB file. So I then downloaded another copy of the image.. Checked the CAB's in the new image. One corrupt CAB, but different to the first.

So I have now created a new Image by replacing the damaged CAB file. All seems to be running OK so far..

Good News:
4 Hours and ~12GB Later - May have a solution!

Bad News:
Could be my HDD on its way out! =(

This of course could be so much easier if MS had posted 10% PAR2 recovery data with the image, "Just in case"...

I look forward to have a play with the new Beta!

Oh, if this does work (and I think it should now) I will create PAR2 data for the CAB files, if any one else is having problems, then please give me a shout and I will be happy to send them to you (rather than you download multiple images as well).

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Outsourced Developers?

Mon, 30 Jul 2007 18:06:13 GMT

OK. One thing that is really bothering me... And I have to say this.

I am working so hard to get myself up to a good standard of development, yet I am still considered by the industry to be "inexperienced". I would however agree with this statement. There are technologies I have yet to get up to speed on, and I will do in due course, but in the meantime, I will continue to work hard and gain experience.

What I do not get, is the huge influx of outsourced developers onto development forums I am involved in. This in itself is fine, I don't care where people are from. What bothers me is that these people are clearly not up to my standard, let alone "the industry's". So why are so many companies outsourcing development to them?

One thing I have really started to get a handle on is the cost of IT, and especially (as it is relevant to me) the cost of developers. I know we are not cheap. But, I fail to see how 10 developers @ 5Kpa (not sure on the avg. developer salary in India) that do not understand basic debugging techniques, object-orientated principles or even the basic language construct can ever produce a product anywhere near the same standard as 1 or 2 (trained) developers @ 30Kpa.

I have recently responded to several forums on posts, where answers are demanded, rather than asked for (I always try to be humble on forums, the people that help me are doing me a favour). And I stare in disbelief at what questions are being asked. "What's a syntax error?!?!?" WHAT!? What sort of a "developer" does not understand the concept of a "syntax error". The difference between syntax and logic errors was one of the very first things I learned waaaay back! I actually find myself seeing another rude post on a forum and "Location: India" asking incredibly basic stuff, that is obviously going into a business application and not wanting to help. This makes me feel terrible!

What are the developer "standards" for these software houses? Are there any?

On top of this, another key fact I have learned (and I am sure any developer will back me up on this) is the importance of translation. The translation of the software requirements into good, solid code. Now, if there are language barriers, and of course there are, this is going to cause trouble at the first hurdle. I've seen some incredible broken-English error messages that are so bad that (having finished laughing) I actually didn't know what the error was!

So, my point is this. You get what you pay for. Thankfully, I think some companies are starting to realise that cheap code is not necessarily good code, and they are starting to bring development back onshore.

I also think this is the case with other IT related jobs (especially support) although, they are not my remit and I would not like to pass to much commentary.

Has anyone else experience this, or is it really just me?

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