Thursday, January 14, 2010

ASP, Error-Handling and Microsoft's Latest Catchphrase

Microsoft's Latest Catchphrase: It may be crap, but at least it is ready installed crap!

What inspired today's rant? Using ASP, of course. The question I had was to how to handle SQL errors. (This article is more than just rant; I will also tell you how to do a couple of essential tasks that ASP makes hard.)

I've been using ASP for a few months, for one particular sub-project. We wanted to minimize the installed components, and as one sub-system already needed IIS, and the required scripting was fairly simple, we decided to go with that instead of installing WAMP (Windows Apache/MySQL/PHP).

I'm using ADODB COM object for the database connectivity to Microsoft SQL Server. I've used the same COM object from PHP before, and errors get thrown as exceptions. I wrap them in try/catch blocks and everything is good. A bit of searching discovered how it works in ASP/VBScript. First exceptions are thrown just the same. Second, there is no try/catch functionality.

Read those two key facts again, and have a good long think about them.

Some more searching discovered things are not quite that bad, and you can handle errors. The first thing you must do is precede your function with "on error resume next". That tells it to ignore errors. Then immediately after any action that might have had an error you do:

if err.Number <> 0 then
'Handle errors here
end if

See here and here.

By the way, to turn off "resume next" mode, you give the almost mystical "On Error Goto 0". And the other thing you need to know is that resume next mode only affects the current function; if you call another function and that function doesn't explicitly "on error resume next" then any error there will terminate the script. Which I suppose is better than the confusion resulting if the flag was global.

As my next piece of evidence let me show you how to do the equivalent of PHP's "s=file_get_contents(fname);" in ASP (due to the afore-mentioned difficulties in error-reporting it returns a blank string if the file does not exist):

Function file_get_contents(fname)
mode=1 'Read-only
set FSO = server.createobject("Scripting.FileSystemObject")
set fp= FSO.OpenTextFile( fname, mode)
set fp= nothing
end if
set FSO = nothing
End Function

Oh, what fun! But I try to be fair, and every language has its good and bad points, so I tried to think up all the good features of ASP. After all, I have actually been writing useful, working code in ASP. The bad points flashed into my mind at every turn, but in the end I did manage to find one good point...

It is already installed, if you are already using IIS.

Which brings us back to that catchphrase that Microsoft is hurriedly trade-marking in 120 countries worldwide: It may be crap, but at least it is ready installed crap!

(By the way, speaking of ready-installed crap, did you know IE6 still has 15-20% market share? And IE6+IE7+IE8 together have 67% share? It was news to me - I thought the browser wars were over and everyone used Firefox, or at least Safari!)

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