ASP.NET Log File - Felix John COLIBRI.

• abstract : an Asp.Net journaling CLASS for debugging and monitoring Web Developments
  
• key words : ASP.NET, log, journal, utility, debugging, trace
  
• software used : Windows XP Home, Delphi 2005
  
• hardware used : Pentium 2.800 Mhz, 512 M memory, 250 G hard disc
  
• scope : Delphi 8 , Delphi 2005, Delphi 2006, Windows
  
• level : Delphi Web Developer
  
• plan :
  
  • Goal of an Asp.Net log file
    
  • The Asp.Net log file class
    
  • Mini Howto
    
  • Improvements
    
  • Download the Sources
    

1 - Goal of an Asp.Net log file

Asp.Net is delivered with all kinds of debugging features. Without rejecting all those tools, we are so used to indented log files that we started to implement them as our first step in the Asp.Net world.

One of the reason is that the file log centralizes all debugging text during the lifetime of a user visit:

• when the user requests a page, the Web Server starts a new AppDomain (a kind of lightweight thread)
  
• when the user clicks on a link, this will start another AppDomain
  

2 - The Asp.Net log file CLASS

2.1 - Writing to a log file

• we create (or open) a FileStream
  
• we create a StreamWriter to write strings
  
• then we call StreamWriter.WriteLine( xxx );
  

2.2 - The UNIT

Here is the constructor:

with the writing method

Usually the project using the log declares a c_log variable, and uses this variable to create and write to the log.

In the Asp.Net case, since each new page lives in a separate AppDomain, this is not convenient. So we use a self sufficient log:

• on page request creates, and uses the log
  
• the other pages simply write to the log
  

Here is the creation global procedure:

and the log writing procedure is:

where the '>' and '<' are a way to indent / unindent the log output

2.3 - Where should we place the Log File ?

Do NOT place the log in the p_xxx\BIN directory. For a complete explanation, see the the BIN changes story below.

2.4 - When should the log be created ?

The sad story is that the mere publishing of those pages demonstrate that following the flow of control during the rendering of a page is not obvious.

We naturally wanted to create the log in the first event which requires a log entry. So we first placed the creation in the main .Aspx tWebForm1.Page_Load or tWebForm1.OnInit events. We later had to investigate Global.Asax, and found out that events in this file were called before the main page. The documentation confirms this in the "HTML Pipeline" descriptions. So we placed the creation in the Global.Asax create event.

2.5 - log example

	start Delphi
	select "file | new | asp.net application"
	Delphi presents the path / file / server dialog
	type the requested information. In our case the project will be located in:     c:\programs\us\web\asp_net\p_asp_net_log_file so the dialog will look like:
	then, in the top right tree project manager, right click the WebForm1.aspx line, and rename the file name "a_asp_net_log_file.aspx"
	the project folder will look like this:
	compile and run to make sure that everyting in correct
	Delphi starts Cassini, loads Internet Explorer which displays our application

	select "Project | Options "
	Delphi opens the Options dialog
	select "Directories"
	Delphi opens the directories tabsheet
	click the "search path" ellipsis and enter the dot_net_units and dot_net_classes pathes

open a Windows Explorer, and create the log path. For instance:   c:\programs\us\web\asp_net\p_asp_net_log_file\_asp_log

	then, in the top right tree project manager, click Global.Asax:
	Delphi opens the file in the Editor
	add the unit in the USES after the implementation
	add the log creation in the Global CONSTRUCTOR (there is a "// TODO: Add any constructor code after InitializeComponent call" that we removed) constructor TGlobal.Create;   begin     inherited;     InitializeComponent;     create_asp_net_log('c:\programs\us\web\asp_net\'         + 'p_asp_net_log_file\_asp_log\the_log.txt');     write_to_asp_net_log('======');     write_to_asp_net_log('log_started');   end; // TGlobal.Create
	compile and run
	click on the the_log.txt file
	NotePad is started and it displays the log content

3 - Mini Howto

• add the u_c_asp_net_log unit to your Asp.Net project. Also add the dependent units (all in the zip below)
  
• add the USES clause to all the .PAS which will either create or write to the log file
  
• create the log destination directory. If you want a new log, remove any existing log.txt
  
• add the log creation in an event called before any log write
  
• add all the log write in your .PAS code
  

4 - Improvements

4.1 - The log in BIN saga

BIN is build by default by Asp.Net. So this is fixed. Then we decided to nest a log\ sub directory in BIN

We then encountered random "Thread Timeout" exceptions, which could not be explained.

Out of despair we went on Google searching for +"asp.net"+thread timeout". After a couple of trials, we hit the following page:

    Strange thread timeout behavior again

This was my lucky day since I somehow browsed this 54 K long search and anguished thread, instead of clicking away after one or two pages, to finally stumble on the following paragraph (near the end, of course - hilite was added):

I had read about this automatic recompilation of .ASPX pages, whith all this shadow copying business and all. But I was miles away from the diagnostic when the exceptions started hitting the application.

I would certainly question Mr CHENG's postscript "Get Secure with www.microsoft.com". Must be some kind of Redmond private joke, I guess. But he did save my day, so, thank you very much, Mr CHENG.

In conclusion: NEVER place any custom file which is updated in the BIN directory.

4.2 - Programming Notes

• Much could be done to improve this log. We could add a display on a web page Label, concatenate the logs etc.

• I'm still not very efficient with the C# notation:
  
  • System.Io.File.Exists instead of the FileExists function
    
  • & File to avoid the reserved FILE
    
  • FileAccess.Write because Java (and therefore C#) does not have decent constants.
    
  But whining and crying is no solution: either stick with Delphi 6, which is fine, or for Asp.Net development, bite the bullet. In this area, the best book still remains the Xavier PACHECO's "Delphi 8 for .Net", which is better than most of the books on Delphi, even the recent Delphi 2006 books where nearly all authors try to cater to both Vcl.Net and Windows Forms developments. Fatal error.

• Using this old log file will certainly look outdated in our time and age of steppers, symbolic debuggers and event logs, but, after over 20 years of developments, I personally have never found a more efficient tool. I used one with the Apple UCSD Pascal, then for 6502 assembler, Prolog, Postscript, 8086 assembler, Delphi, of course. And the first thing for .Net I developed was, of all things, the log file.
  

5 - Download the Sources

• asp_net_log_file.zip: the full project with the unit and the dependent units(12 K)
  

The .ZIP file(s) contain:

• the main program (.DPR, .DOF, .RES), the main form (.PAS, .DFM), and any other auxiliary form
  
• any .TXT for parameters, samples, test data
  
• all units (.PAS) for units
  

• are self-contained: you will not need any other product (unless expressly mentioned).
  
• for Delphi 6 projects, can be used from any folder (the pathes are RELATIVE)
  
• will not modify your PC in any way beyond the path where you placed the .ZIP (no registry changes, no path creation etc).
  

• create or select any folder of your choice
  
• unzip the downloaded file
  
• using Delphi, compile and execute
  

The Pascal code uses the Alsacian notation, which prefixes identifier by program area: K_onstant, T_ype, G_lobal, L_ocal, P_arametre, F_unction, C_lasse etc. This notation is presented in the Alsacian Notation paper.

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6 - The author