threading and UI calls

[Jim H]

About a year back I posted a question and eventually implemented the
following code in an event handler as a result:

object[] some_args = new object[1];
some_args[0] = my_event_args.r esults;
ISynchronizeInv oke lSync = this as ISynchronizeInv oke;
if(lSync == null)
{// UI Thread
UIDelegate.Dyna micInvoke(some_ args);
}
else
{// Worker thread
this.Invoke(UID elegate, some_args);
}

Reading the code now I'm questioning it. Can lSync ever be null if the code
is in a WinForm derived class. Other examples I am seeing all do a check of
InvokeRequired before calling Invoke. Since I am in the form code lSync can
never be null, correct? Therefore, in my current code, I am always calling
this.Invoke. I have changed the code to check InvokeRequiredb efore calling
Invoke. If InvokeRequired is false I just make the call directly.

My new code:
object[] some_args = new object[1];
some_args[0] = my_event_args.r esults;
ISynchronizeInv oke lSync = this as ISynchronizeInv oke;

if(lSync.Invoke Required)
{// Worker thread
lSync.Invoke(UI Delegate, some_args);
}
else
{//gui thread
MyHandler(my_ar gs.results);
}

Is this correct? This just seems to have less overhead than always calling
invoke.

Thanks,
jim

[Brian Gideon]

Re: threading and UI calls

Jim,

You are right. The first example is wrong, but the second is correct.

Brian

Jim H wrote:[color=blue]
> About a year back I posted a question and eventually implemented the
> following code in an event handler as a result:
>
> object[] some_args = new object[1];
> some_args[0] = my_event_args.r esults;
> ISynchronizeInv oke lSync = this as ISynchronizeInv oke;
> if(lSync == null)
> {// UI Thread
> UIDelegate.Dyna micInvoke(some_ args);
> }
> else
> {// Worker thread
> this.Invoke(UID elegate, some_args);
> }
>
> Reading the code now I'm questioning it. Can lSync ever be null if the code
> is in a WinForm derived class. Other examples I am seeing all do a check of
> InvokeRequired before calling Invoke. Since I am in the form code lSync can
> never be null, correct? Therefore, in my current code, I am always calling
> this.Invoke. I have changed the code to check InvokeRequiredb efore calling
> Invoke. If InvokeRequired is false I just make the call directly.
>
> My new code:
> object[] some_args = new object[1];
> some_args[0] = my_event_args.r esults;
> ISynchronizeInv oke lSync = this as ISynchronizeInv oke;
>
> if(lSync.Invoke Required)
> {// Worker thread
> lSync.Invoke(UI Delegate, some_args);
> }
> else
> {//gui thread
> MyHandler(my_ar gs.results);
> }
>
> Is this correct? This just seems to have less overhead than always calling
> invoke.
>
> Thanks,
> jim[/color]

[Nicholas Paldino [.NET/C# MVP]]

Re: threading and UI calls

Jim,

Form derives ultimately from Control, which implements
ISynchronizeInv oke. You don't have to check to see if it implements it.

As for your code, you don't have to cast to ISynchronizeInv oke, as
Control/Form implements the interface implicitly (so you can call it right
off the "this" reference).

Hope this helps.


--
- Nicholas Paldino [.NET/C# MVP]
- mvp@spam.guard. caspershouse.co m

"Jim H" <jimh@nospam.no spam> wrote in message
news:Ot$LJl3mGH A.5056@TK2MSFTN GP04.phx.gbl...[color=blue]
> About a year back I posted a question and eventually implemented the
> following code in an event handler as a result:
>
> object[] some_args = new object[1];
> some_args[0] = my_event_args.r esults;
> ISynchronizeInv oke lSync = this as ISynchronizeInv oke;
> if(lSync == null)
> {// UI Thread
> UIDelegate.Dyna micInvoke(some_ args);
> }
> else
> {// Worker thread
> this.Invoke(UID elegate, some_args);
> }
>
> Reading the code now I'm questioning it. Can lSync ever be null if the
> code is in a WinForm derived class. Other examples I am seeing all do a
> check of InvokeRequired before calling Invoke. Since I am in the form
> code lSync can never be null, correct? Therefore, in my current code, I
> am always calling this.Invoke. I have changed the code to check
> InvokeRequiredb efore calling Invoke. If InvokeRequired is false I just
> make the call directly.
>
> My new code:
> object[] some_args = new object[1];
> some_args[0] = my_event_args.r esults;
> ISynchronizeInv oke lSync = this as ISynchronizeInv oke;
>
> if(lSync.Invoke Required)
> {// Worker thread
> lSync.Invoke(UI Delegate, some_args);
> }
> else
> {//gui thread
> MyHandler(my_ar gs.results);
> }
>
> Is this correct? This just seems to have less overhead than always
> calling invoke.
>
> Thanks,
> jim
>[/color]