Async Execution and Thread-Safety

[Stefan Hoffmann]

hi @all,

I've have this working piece of code in an async callback function used:

private void SetCount()
{
if (listView.InvokeRequired)
{
listView.Invoke((MethodInvoker)(() => SetCount()));
}
else
{
listItem.SubItems[1].Text = list.Count.ToString();
}
}

Can this produce an infinite loop under some circumstances?

I've seen similar in the net, but no comments about termination...


mfG
--> stefan <--

 

[Alberto Poblacion]

I've have this working piece of code in an async callback function used:

private void SetCount()
{
if (listView.InvokeRequired)
{
listView.Invoke((MethodInvoker)(() => SetCount()));
}
else
{
listItem.SubItems[1].Text = list.Count.ToString();
}
}

Can this produce an infinite loop under some circumstances?

I don't think so. InvokeRequired is True when the code is executing in a
different thread from that one that created the form. The Invoke method will
marshall execution into the main thread, and therefore InvokeRequired will
become False, so the second try will get into the "else" and not produce an
infinite loop.

 

[Stefan Hoffmann]

hi Peter,

By the way, I really, _really_, don't like the "InvokeRequired"
pattern. I wish MSDN had never suggested it. The Invoke() method
already has to do the same check, and it correctly deals with the
condition where InvokeRequired is false by just calling the invoked
delegate directly. So, your example could much more cleanly be written
like this:

private void SetCount()
{
listView.Invoke((MethodInvoker) delegate
{
listItem.SubItems[1].Text = list.Count.ToString();
});
}

This is really good idea. Thanks.


mfG
--> stefan <--