Are All the Static/Shared Methods in .NET Thread Safe? - Page 2

Laser Lu

I was often noted by Thread Safety declarations when I was reading .NET Framework Class Library documents in MSDN.
The declaration is usually described as 'Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.'
So, does this mean All the static/shared methods written in .NET compatible programming language, such as C#, VB.NET, are guaranteed to be synchronized and thread safe? Or else, we still need to implement our custom code to ensure the thread-safty for static methods?

Mar 20 '07

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2785

Laser Lu

Ok, tank you.:)

"Alberto Poblacion" <ea************ *************** ***@poblacion.o rgwrote
in message news:ey******** *****@TK2MSFTNG P02.phx.gbl...

"Laser Lu" <la******@163.c omwrote in message
news:OO******** ******@TK2MSFTN GP02.phx.gbl...
>[...] The declaration is usually described as
'Any public static (Shared in Visual Basic) members
of this type are thread safe. Any instance members
are not guaranteed to be thread safe.'
So, does this mean All the static/shared methods written
in .NET compatible programming language, such as C#,
VB.NET, are guaranteed to be synchronized and thread
safe? Or else, we still need to implement our custom
code to ensure the thread-safty for static methods?

The programming guidelines from Microsoft recommend that you make all
your public static methods thread-safe, and indeed they have followed
those guidelines in the classes that they have provided with the
Framework.
However, this is not automatic. Just marking a method as static does
not guarantee that it will be tread-safe. you still have to examine your
code and see if there is something in it that could be affected, such as a
shared variable that could be accessed by two threads, and apply adequate
locking mechanisms to ensure its safety.

Mar 21 '07 #11

Laser Lu

Thanks!

"William Stacey [C# MVP]" <wi************ @gmail.comwrote in message
news:Op******** ******@TK2MSFTN GP03.phx.gbl...

Any method (static or otherwise) that is called by multiple threads and
uses
any shared state must be aware of syncronization and take require action
depending on needs. Static != thread safe.

--
William Stacey [C# MVP]
"Mike Labosh" <mlabosh_at_hot mail_dot_comwro te in message
news:eD******** ******@TK2MSFTN GP06.phx.gbl...
|The declaration is usually described as 'Any public static (Shared in
| Visual Basic) members of this type are thread safe. Any instance members
are
| not guaranteed to be thread safe.'
| So, does this mean All the static/shared methods written in .NET
compatible
| programming language, such as C#, VB.NET, are guaranteed to be
synchronized
| and thread safe?
|
| Yes. I have never heard of a static (Shared) method *not* being
| thread-safe.
|
| The reason that static / Shared methods are always thread-safe is
because
| there is no instance of a class, and therefore, no member variables for
| threads to stomp on in contradictory ways.
|
| Any local variables inside a static / Shared method exist locally within
the
| particular stack frame of the calling code on the calling thread, and
| therefore, will never conflict with multiple threads simultaneously
hitting
| the same method with local variables.
| --
|
| Peace & happy computing,
|
| Mike Labosh, MCSD MCT
| Owner, vbSensei.Com
|
| "Escriba coda ergo sum." -- vbSensei
|
|

Mar 21 '07 #12

Laser Lu

Thanks for your reply. Now, I've had a better understanding based on your
explaination.:)

"Anthony Paul" <an**********@g mail.comwrote in message
news:11******** **************@ e65g2000hsc.goo glegroups.com.. .

Here's the deal... the only difference (that I am aware of) between
static and instance methods is that instance methods pass the "this"
pointer silently while static methods do not; that's it. I think that
the reason why static methods have been marked as "thread safe" is
that they are assuming that, since the method is static, you won't be
accessing any shared-state as you most likely would in an instance
method. Both instance methods and static methods *are* thread-safe as
long as you don't access any shared-state (eg. instance/static fields)
since each thread has its own local stack.

In short, if you have a multi-threaded application that needs to
access shared-state, you need to synchronize all access via a locking
mechanism such as lock, mutexes, monitor, etc...

Here's a link that might help : http://www.odetocode.com/Articles/313.aspx

Regards,

Anthony

On Mar 20, 4:08 am, "Laser Lu" <laser...@163.c omwrote:
>I was often noted by Thread Safety declarations when I was reading .NET
Framework Class Library documents in MSDN.
The declaration is usually described as 'Any public static (Shared in
Visual Basic) members of this type are thread safe. Any instance members
are not guaranteed to be thread safe.'
So, does this mean All the static/shared methods written in .NET
compatible programming language, such as C#, VB.NET, are guaranteed to be
synchronized and thread safe? Or else, we still need to implement our
custom code to ensure the thread-safty for static methods?

Mar 21 '07 #13

Cor Ligthert [MVP]

In my idea to the best answer

Mar 21 '07 #14

Laser Lu

A-ha, quite agree with u. The most brief and definite answer.:)

"Cor Ligthert [MVP]" <no************ @planet.nlwrote in message
news:eW******** ********@TK2MSF TNGP03.phx.gbl. ..

In my idea to the best answer

Mar 21 '07 #15

William Stacey [C# MVP]

They are marked thread-safe, only when the *author (in this case MS) has
taken the time to verify they are thread safe (which is easy if they don't
touch shared data). As most statics in the framework (not sure if all are)
are documented with the thread safe attribute, it is easy to assume that is
some kind of special gaureentee all statics give - which is not the case.
You can easily make a non thread safe static method via bug or on purpose.

--
William Stacey [C# MVP]
"Anthony Paul" <an**********@g mail.comwrote in message
news:11******** **************@ e65g2000hsc.goo glegroups.com.. .
| Here's the deal... the only difference (that I am aware of) between
| static and instance methods is that instance methods pass the "this"
| pointer silently while static methods do not; that's it. I think that
| the reason why static methods have been marked as "thread safe" is
| that they are assuming that, since the method is static, you won't be
| accessing any shared-state as you most likely would in an instance
| method. Both instance methods and static methods *are* thread-safe as
| long as you don't access any shared-state (eg. instance/static fields)
| since each thread has its own local stack.
|
| In short, if you have a multi-threaded application that needs to
| access shared-state, you need to synchronize all access via a locking
| mechanism such as lock, mutexes, monitor, etc...
|
| Here's a link that might help : http://www.odetocode.com/Articles/313.aspx
|
| Regards,
|
| Anthony
|
| On Mar 20, 4:08 am, "Laser Lu" <laser...@163.c omwrote:
| I was often noted by Thread Safety declarations when I was reading .NET
Framework Class Library documents in MSDN.
| The declaration is usually described as 'Any public static (Shared in
Visual Basic) members of this type are thread safe. Any instance members are
not guaranteed to be thread safe.'
| So, does this mean All the static/shared methods written in .NET
compatible programming language, such as C#, VB.NET, are guaranteed to be
synchronized and thread safe? Or else, we still need to implement our custom
code to ensure the thread-safty for static methods?
|
|

Mar 21 '07 #16

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