Implementing Singleton in ASP.Net

I was not sure where to post this question. This discussion group seemed most
appropriate. If any one things otherwise can they please redirect me to the
right discussion group?

Here qoes the question anyway...

I have built an ASP.net application that uses the singleton pattern to keep
one instance of the user object for the life time of a user request. My
problem arises when two or more users try to access the same singleton.

Since ASP.net uses one process for the entire lifetime of the application
and the threads are reused for request hence i implemented the singleton
using the HttpContext Session. My beleive was that for every request from the
user there would be one singleton object instantiated. If this is the case
then why are the users getting crossed while browsing the application.

The singleton code is a follows;
------------------------------------------------------------ --------------------------------
private static object syncRoot = new object();
string SESSION_SINGLETON = "iPlan.Domain.iPlanUser";
public static iPlanUser GetCurrentSingleton()
{
iPlanUser single = null;

if(HttpContext.Current.Session[SESSION_SINGLETON] == null)
{
lock(syncRoot)
{
iPlanUser single = new iPlanUser();
HttpContext.Current.Session[SESSION_SINGLETON] = single;
}
}
else
{
single = (iPlanUser)HttpContext.Current.Session[SESSION_SINGLETON];
}

return single;

}//End Get Current Singleton

public static void Dispose()
{
//Clean up this object so that the garbage collector (GC) can reclaim
memory space
System.Web.HttpContext.Current.Session.Remove(SESSION_SINGLE TON);
}//End Dispose

------------------------------------------------------------ --------------------------------

Can anyone please help me understand this code a bit better or tell me what
i am not doing correctly.

Thanx
RaVs

Re: Implementing Singleton in ASP.Net

Your question involves ASP.Net code, which instantly removes it from the
realm of IIS into the realm of ASP.Net . Not certain what your question has
to do with IIS Security...

Try:
microsoft.public.dotnet.framework.aspnet
www.asp.net Forums


I think you also want to read this blog entry to get an idea of how Session
State works (conceptually) because some of your terminology seems confused
(to me):
http://blogs.msdn.com/david.wang/archive/2005/09/19/Why_do_I _lose_ASP_Session_State_on_IIS6.aspx


Also, your implementation of GetCurrentSingleton() is flawed and has a race
condition. You need to obtain the lock PRIOR to examining the singleton
value, and release it when you are done examining/modifying its value.
Otherwise, two threads can simultaneously examine the singleton value prior
to obtaining the lock and both will succeed...

--
//David
IIS
http://blogs.msdn.com/David.Wang
This posting is provided "AS IS" with no warranties, and confers no rights.
//
"RaVs" wrote in message
news:8D2EB2B6-D7BF-4D0E-B036-5165FAB3A6D7@microsoft.com...
I was not sure where to post this question. This discussion group seemed
most
appropriate. If any one things otherwise can they please redirect me to the
right discussion group?

Here qoes the question anyway...

I have built an ASP.net application that uses the singleton pattern to keep
one instance of the user object for the life time of a user request. My
problem arises when two or more users try to access the same singleton.

Since ASP.net uses one process for the entire lifetime of the application
and the threads are reused for request hence i implemented the singleton
using the HttpContext Session. My beleive was that for every request from
the
user there would be one singleton object instantiated. If this is the case
then why are the users getting crossed while browsing the application.

The singleton code is a follows;
------------------------------------------------------------ ----------------
----------------
private static object syncRoot = new object();
string SESSION_SINGLETON = "iPlan.Domain.iPlanUser";
public static iPlanUser GetCurrentSingleton()
{
iPlanUser single = null;

if(HttpContext.Current.Session[SESSION_SINGLETON] == null)
{
lock(syncRoot)
{
iPlanUser single = new iPlanUser();
HttpContext.Current.Session[SESSION_SINGLETON] = single;
}
}
else
{
single = (iPlanUser)HttpContext.Current.Session[SESSION_SINGLETON];
}

return single;

}//End Get Current Singleton

public static void Dispose()
{
//Clean up this object so that the garbage collector (GC) can reclaim
memory space
System.Web.HttpContext.Current.Session.Remove(SESSION_SINGLE TON);
}//End Dispose

------------------------------------------------------------ ----------------
----------------

Can anyone please help me understand this code a bit better or tell me what
i am not doing correctly.

Thanx
RaVs