How often does the constructor run?

  • Thread starter Thread starter Joe Fallon
  • Start date Start date
J

Joe Fallon

I have a Shared class with a New constructor that initializes some Shared
properties.

One of the steps involves a hit to the database.
My tests show that when called by a WinForms app, the constructor only runs
once.
All calls to the class after this do not casues the construtor to run again.
This means it is a one time hit to the database to load these properties.
1. Can someone confirm this?

When I start and stop the WinForms app the Shared class needs to be
initialized on each re-start.
This makes sense.
My question is how would this class behave as a .dll on an application
server?
What would cause it to load and unload?
I guess the load would be caused by the first call from another class.

But if I change the Config file how do I get it to unload and re-load to
re-read the config file?
 
Joe,
If you have a Shared Sub New, it will be called once when that class is
first referenced (when the code is loaded basically).

If you create new AppDomains, I understand that it will be called once for
each AppDomain. However I have not done a lot with AppDomains so I can not
say for certain either way.
My question is how would this class behave as a .dll on an application
server?
Click to expand...
What do you mean by application server?
What would cause it to load and unload?
Click to expand...
The only way I can think of is to load & unload the class in new AppDomains,
however I have not done a lot with AppDomains...
But if I change the Config file how do I get it to unload and re-load to
re-read the config file?
Click to expand...
ASP.NET does this, I believe what it does is to use a
System.FileSystem.Watcher to watch the config file, if the config file
changes it creates a new AppDomain and transfers control to it...

Note, AppDomains also allow you to specify which config file you should use.

Hope this helps
Jay
 
Jay,
I meant IIS when I used the term application server.

So your comment about ASP.Net monitoring the Web.config file sounds like the
behavior I need.
e.g. If I change the Config file then the next call to the class will cause
the constructor to run once.
(I have seen this with regular WebForms so I hope it will work the same
way.)

I will give it a try later.

Thanks.
 
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