singleton

Probably a newbie questions...
If I have a singleton class which read and write to a database, what happens
if 2 or more clients call the same methods at the same time?
If one method is:
public DataSet GetData(string sql_query){
some database operations...
return _dataset;
}
and client 1 call:
GetData("select * from users");
and client 2 call:
GetData("select * from cars");
is there any possibilities that client 1 receives the cars dataset or
viceversa?
Thanks, in advance
FabioHello Fabio R." fabio81(at)yahoo.com,
As long as your GetData method does not modify/user any class level variable
s,
you should be threadsafe.
Matt Berther
http://www.mattberther.com

> Probably a newbie questions...
> If I have a singleton class which read and write to a database, what
> happens
> if 2 or more clients call the same methods at the same time?
> If one method is:
> public DataSet GetData(string sql_query){
> some database operations...
> return _dataset;
> }
> and client 1 call:
> GetData("select * from users");
> and client 2 call:
> GetData("select * from cars");
> is there any possibilities that client 1 receives the cars dataset or
> viceversa?
> Thanks, in advance
> Fabio
I was wondering the same thing.
Does anyone know the scope of the class?
What about on multiple processors?
Separate threads/appdomains etc ?
Thanks
-Dwight
I have a couple articles discussing thread safety and static memebers:
http://odetocode.com/Articles/313.aspx
http://odetocode.com/Articles/314.aspx
From the code you've outlines you should not have any problems, as the
code appears to only use variables local to the method.
Scott
http://www.OdeToCode.com/blogs/scott/
On Thu, 27 Jan 2005 01:02:40 +0100, "Fabio R." <fabio81(at)yahoo.com>
wrote:

>Probably a newbie questions...
>If I have a singleton class which read and write to a database, what happen
s
>if 2 or more clients call the same methods at the same time?
>If one method is:
>public DataSet GetData(string sql_query){
>some database operations...
>return _dataset;
>}
>and client 1 call:
> GetData("select * from users");
>and client 2 call:
> GetData("select * from cars");
>is there any possibilities that client 1 receives the cars dataset or
>viceversa?
>Thanks, in advance
>Fabio
>
Thanks to all.
So, a "design" question regarding this topic:
it's better to have, in example, all the 10/15 classes of the data layer as
singleton or let the users create their own istances at every request or put
all the istance in a "session singleton" as in
http://aspalliance.com/articleViewer.aspx?aId=70 article?
The classes has only methods with locale variables.
What's better for the server memory/performance?
Fabio

> From the code you've outlines you should not have any problems, as the
> code appears to only use variables local to the method.
> If I have a singleton class which read and write to a database, what
> happens if 2 or more clients call the same methods at the same time?
In fact, nothing on a computer happens at the same time. A computer can do
precisely one calculation at a time. Multi-tasking is accomplished by
looping in the OS. Network requests are queued. And each client is uniquely
identified within their own thread. So, nothing special happens when 2 or
more clients call the same methods "at the same time."
You might ask the same question of your Operating System. It is
multi-tasking, and many applications may be making API calls to the OS "at
the same time." However, each application somehow manages to keep track of
its own "stuff."
HTH,
Kevin Spencer
Microsoft MVP
.Net Developer
Neither a follower nor a lender be.
"Fabio R." <fabio81(at)yahoo.com> wrote in message
news:u6wv4NABFHA.2428@.TK2MSFTNGP14.phx.gbl...
> Probably a newbie questions...
> If I have a singleton class which read and write to a database, what
> happens if 2 or more clients call the same methods at the same time?
> If one method is:
> public DataSet GetData(string sql_query){
> some database operations...
> return _dataset;
> }
> and client 1 call:
> GetData("select * from users");
> and client 2 call:
> GetData("select * from cars");
> is there any possibilities that client 1 receives the cars dataset or
> viceversa?
> Thanks, in advance
> Fabio
>