Re: public static/shared read only properties in global.asax
From: Gary Bagen (garbage400_at_hotmail.com)
Date: 03/27/04
- Next message: Andrei Suvorov: "apsnet_wp.exe non-default identity vs. System.Web.Mail.SmtpMail"
- Previous message: Landley: "Re: Memory Clean Up"
- In reply to: John Saunders: "Re: public static/shared read only properties in global.asax"
- Messages sorted by: [ date ] [ thread ]
Date: 26 Mar 2004 16:01:54 -0800
Thanks for the reply, this really helps.
I am trying to simplify the use of the Session, Application and Cache
objects for our developers. Most of our developers are just breaking
the ice with ASP let alone ASP.NET. I'd like to make the applications
more programmable and readable by using Global.StrongName instead of
CType(Application("Icouldspellthiswrong"),ObjectType)
However, the code to implement synchronization is probably too complex
to introduce at this point.
So what I am thinking is having application-wide data load into the
Cache on Application Start (just like the data from Web.Config) and
change those properties to Read Only. As each application instance
gets its own Cache object, we should be safe there.
For variables that the developer wanted to update I was thinking of
wrapper properties over the Application and Session objects. As these
guys having multithreading support built in, could I accomplish the
following?
'Using the Application object
Public Shared Property ReadWriteValue() As Integer
'Use the Application object as it handles reading and
'writing of values in a multithreaded environment.
Get
Return CType(HttpContext.Current.Application("intReadWriteValue"),
Integer)
End Get
Set(ByVal Value As Integer)
HttpContext.Current.Application("intReadWriteValue") =
Value
End Set
End Property
'Using the Session object (this property could also be moved to the
specific page(s) that use the dataset)
Public Shared Property ReadWriteUserDataset() As DataSet
'Use the Session object as it handles reading and
'writing of values in a multi-threaded environment.
Get
Return CType(HttpContext.Current.Session("dsUserDataset"),
DataSet)
End Get
Set(ByVal Value As DataSet)
HttpContext.Current.Session("dsUserDataset") = Value
End Set
End Property
"John Saunders" <john.saunders at SurfControl.com> wrote in message news:<uM4KCU2EEHA.2732@tk2msftngp13.phx.gbl>...
> "Gary Bagen" <garbage400@hotmail.com> wrote in message
> news:8b702e36.0403260925.19424909@posting.google.com...
> > If I add a shared/static read only property to the Global class of
> > global.asax, do I need to implement thread locking like the
> > Application object does?
>
> Any time you can have multiple threads, especially multiple page requests,
> accessing the same object, you have to handle any synchronization issues.
>
> ...
>
> > Public Class Global
> > Inherits System.Web.HttpApplication
> >
> > Private Shared sLocalTitle As String
> >
> > Public Shared ReadOnly Property Title() As String
> > Get
> > 'This was initialized on application_start
> > Return sLocalTitle
> > End Get
> > End Property
>
> In this case, you don't need any locking, since the property is read-only
> and since strings are immutable. The only possible issue would be a
> situation where the application is restarting and one thread gets the old
> title while Application_Start is setting the new one. I'm not sure whether
> ASP.NET prevents this or not for page request threads, but it surely can't
> prevent it for threads you may spawn from a page request.
>
> ...
>
> > Public Shared ReadOnly Property BookList() As DataSet
> > Get
> > Dim dsBookList As DataSet
> >
> > 'Is any thread locking required here? Regardless or dependant on using
> > the
> > 'Cache object?
>
> Yes. Even if only your code is touching Cache("dsBookList"), you still have
> an issue if more than one thread is calling the property while
> Cache("dsBookList") is Nothing. What happens if two threads see dsBookList
> as Nothing and both execute "dsBookList = New DataSet"? That's a classic
> race condition, like "i = i + 1".
>
> Of course, you also need to use locking if you modify the dataset itself.
- Next message: Andrei Suvorov: "apsnet_wp.exe non-default identity vs. System.Web.Mail.SmtpMail"
- Previous message: Landley: "Re: Memory Clean Up"
- In reply to: John Saunders: "Re: public static/shared read only properties in global.asax"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
