You would need to lock as changing the items is not atomic (providing
you want readers to always be in sync i.e. that count and money were
changed at the same time.. but as I said above lock on a private
object don't lock on "this"
Depending on your usage you might also want to consider doing
something like making a value object (has 2 fields in it) and
replacing the value object as an atomic action (but this would only be
useful if you had ALOT of reads and relatively few writes). It would
require the creation of a new object but you could avoid locking on
all of the reads (again it really depends on usage).
Cheers,
Greg
On 8/10/06, Eddie Lascu <[EMAIL PROTECTED]> wrote:
Hi Gregory,
I tried to simplify the class and by doing that, my problem mandates a
simpler solution. Here is a more accurate version of the class:
public sealed class CCTxBatch
{
public CCTxBatch(string strTerminalId)
{
strTerminalId_ = strTerminalId;
}
public int VisaTransactionsCount
{
get
{
return nVisaTxCount_;
}
}
public double VisaTransactionsAmount
{
get
{
return dVisaTxTotalAmount_;
}
}
// next ones here
public void ResetCountsAndTotals()
{
nVisaTxCount_ = 0;
dVisaTxTotalAmount_ = 0.0;
nAmexTxCount_ = 0;
dAmexTxTotalAmount_ = 0.0;
nMCardTxCount_ = 0;
dMCardTxTotalAmount_ = 0.0;
}
public void AddVisaTx( double dAmount )
(
nVisaTxCount_++;
dVisaTxTotalAmount_ += dAmount;
}
public void AddAmexTx( double dAmount )
(
nAmexTxCount_++;
dAmexTxTotalAmount_ += dAmount;
}
public void AddMCardTx( double dAmount )
(
nMCardTxCount_++;
dMCardTxTotalAmount_ += dAmount;
}
int nVisaTxCount_;
double dVisaTxTotalAmount_;
int nAmexTxCount_;
double dAmexTxTotalAmount_;
int nMCardTxCount_;
double dMCardTxTotalAmount_;
string strTerminalId_;
}
I want to have a single lock for all members, because there are yet other
methods that can change multiple pairs. The methods do not return anything,
so I can have all the code inside the method wrapped into a lock(this). I
was curios about the properties.
Regards,
Eddie
-----Original Message-----
From: Discussion of advanced .NET topics.
[mailto:[EMAIL PROTECTED] Behalf Of gregory young
Sent: Thursday, August 10, 2006 6:07 PM
To: [email protected]
Subject: Re: [ADVANCED-DOTNET] Multithread-safe classes
Yes your code will still work fine. There are however some huge
differences between this code and the original.
1) inlining will not be performed since you have put the lock in (this
will result in a (relatively) significant performance hit compared to
the original)
2) In some cases you will have a memory barrier
3) You don't need a critical section in this case (see explanation below)
4) You should be locking on a private lock object as opposed to
locking on "this"
An alternative which you should consider would be
public sealed class MyClass
{
public MyClass(string strValue)
{
strMyField_ = strValue;
}
public string MyField
{
get
{
return strMyField_;
}
}
volatile string strMyField_;
}
This will inline properly and offers nearly identical behavior as your
first example without the overhead you are introducing with a critical
section. This can only be used on items that are the size of a
reference or smaller. The reason you can do this is that anything the
size of a reference or smaller is assured to be changed in an atomic
fashion where you would not need to actually define a critical
section. If the size is over the size of a reference you would then
need to lock in order to insure only one thread at a time is dealing
with the data.
On 8/10/06, Eddie Lascu <[EMAIL PROTECTED]> wrote:
> I want to make my class multithread safe. What's the effect of writing
> something like this:
>
> public sealed class MyClass
> {
> public MyClass(string strValue)
> {
> strMyField_ = strValue;
> }
>
> public string MyField
> {
> get
> {
> lock(this)
> {
> return strMyFieldId_;
> }
> }
> }
>
> string strMyField_;
> }
>
> I know "lock" injects the "finally" block into the CIL, but is that
executed
> if the return is before?
>
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--
If knowledge can create problems, it is not through ignorance that we
can solve them.
Isaac Asimov
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View archives and manage your subscription(s) at http://discuss.develop.com
===================================
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View archives and manage your subscription(s) at http://discuss.develop.com
--
If knowledge can create problems, it is not through ignorance that we
can solve them.
Isaac Asimov
===================================
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View archives and manage your subscription(s) at http://discuss.develop.com
