Event Handler

  • Thread starter Thread starter Anders Eriksson
  • Start date Start date
A

Anders Eriksson

Hello,

I use an COM server that creates a number of events. I have created a class
that controls the COM server and that receives the events, it's called
LaserCtrl. This works!

I have a form that uses LaserCtrl and I want to update a textbox in the form
from LaserCtrl. The constructor of LaserCtrl looks like this

private TextBox msg;

public LaserCtrl(TextBox m)
{
msg = m;
}

From a normal method in LaserCtrl this works perfectly
msg.Text = "my nice message";

BUT from the EventHandler method nothing happens! I'm guessing that this is
because the eventhandler method is in another thread?

How do I solve this?

// Anders
--
English is not my first language, so any
insults or strangeness is due to the translation!

--
--
Anders Eriksson
DC Lasersystem
Software Engineer
073 029 45 74
(e-mail address removed)
 
Anders Eriksson said:
From a normal method in LaserCtrl this works perfectly
msg.Text = "my nice message";

BUT from the EventHandler method nothing happens! I'm guessing that this
is because the eventhandler method is in another thread?
Click to expand...

Yes, if the event handler is running in another thread, you have to
marshall execution into the thread that created the control before you can
change it. One way to do this is by means of its Invoke method:

msg.Invoke(new MethodInvoker(WriteMyText));
....
private void WriteMyText()
{
msg.Text = "my nice message";
}
 
Hello Alberto,
Yes, if the event handler is running in another thread, you have to
marshall execution into the thread that created the control before you can
change it. One way to do this is by means of its Invoke method:

msg.Invoke(new MethodInvoker(WriteMyText));
...
Click to expand...

Two questions.
1. The msg.Invoke should I call it from my eventhandler?
2. How would I do this if I need to have two parameters? E.g
WriteMyText(String msg, Boolean clr)

// Anders
 
Anders Eriksson said:
Two questions.
1. The msg.Invoke should I call it from my eventhandler?
2. How would I do this if I need to have two parameters? E.g
WriteMyText(String msg, Boolean clr)
Click to expand...

1. Yes, you call theControl.Invoke from the code that is running in the
other thread, in this case your eventhandler.

2. Invoke takes actually a System.Delegate parameter, so you can use any
delegate instead of MethodInvoker. I am showing below some code that works
with any version of C# including 1.0, but if you have a newer version you
can simplify the code by means of anonymous delegates or lambdas.

delegate void MyInvoker(String msg, Boolean clr);
....
msg.Invoke(new MyInvoker(MyRoutine), new object[]{valueformsg,
valueforclr});
....
private void MyRoutine(String msg, Boolean clr)
{
...
}
 
Back
Top