eventhandling

[Techno]

*sigh*

so stressful.

I cannot get the idea on how to raise events! how????

I have:

MainForm
ClassA (Worker thread)
ClassB (can be called from worker thread or from MainForm)

MainForm has a method which updates the status of a label (status text)
This will be changed from ClassA and ClassB (Mainly ClassA)

How can I create an eventhandler and raise it so that the main form, when event was raised, can change the status text?

[MrPolite]

hello? I wrote you an extensive example before
http://www.vbforums.com/showthread.php?t=357956

[Mike Hildner]

Here's a quick example project. Not using .Invoke, which I guess you should. Still, it works.

Trickier than I thought, because one needs to (I guess) instantiate the class before you can register with the event, so the constructor can't do anything that would tie things up.

Mike

[Techno]

Thanks very much guys i will look into this

I appreciate the extensive reply MR.Polite :) I just cant seem to get the idea of it. I am using .NETCF so invoking is a bit tricky (but not much)

I just dont know how to properly invoke the event from the worker thread!

Main form:



this.OnStatusChange += new TheStatusChange(frmMain_OnStatusChange);
public delegate void TheStatusChanged();
public event TheStatusChanged OnStatusChange;
public string theStatusChange;

..
..
private void ChangeStatus()
{
this.lblCurrentStatus.Text = this.theStatusChange;
}

private void frmMain_OnStatusChange()
{
this.ChangeStatus();
}


ClassA

//this class is instantiated by the main form
//somemethod
//create new thread and execute ClassB



Worker Thread:


//ClassB
public delegate void TheStatusChangedEventHandler();

..
//some method

//dont know what to put here to invoke the eventhandler on the main form from this worker thread



I dont know if I am doing this correctly or not.
I will check out the attached example as well as re read Mr.Polite's reply/in depth explanation! :)
please, any more tips do post!

[MrPolite]

hmm not sure if I get the idea but you could try this:D
remove that delegate from the worker thread.

in the worker thread, add this (the same as the main form's event)
public event TheStatusChanged OnStatusChange;
now in the main form, replace that line with this

private event TheStatusChanged m_OnStatusChange;
public event TheStatusChanged OnStatusChange
{
add
{
// add the event handler both to this class and to the worker thread
m_OnStatusChange += value;
workerThreadHere.OnStatusChange += value;
}
remove
{
m_OnStatusChange -= value;
workerThreadHere.OnStatusChange -= value;
}
}


now inside the worker thread, to raise the event do this:

if (OnStatusChange != null)
OnStatusChange();

[Techno]

hmmm

I will try that but it kinda isnt possible.

Sorry, I should have explained more in depth of what/how the app is coded.

mainform (has label)
ConnMan
CommunicationMan
IncomingDataMan

When button is clicked on main form, it creates a new instance of ConnMan.
In ConnMan constructor it creates an instance of CommunicationMan.
In CommunicationMan it creates an instance of IncomingDataMan

A thread is created in ConnMan and executes a method in CommunicationMan.

in that method in CommunicationMan it calls a method everytime (while true) in IncomingDataMan.

IncomingDataMan deals with incoming data and sets the status of the incoming data (like a description) on the main form in a label, or by a public string variable on mainform.

instead of doing this FROM incomingDataMan:

this.theMainForm.lblCurrentStatus = "sometext";


I prefer to use events/delegates simply because its thread safer and won't cause strange behaviour and frankly its the best way to go.

This is what I like to know is on how to make events and invoke them/make them "raised" in the main form from the incomingDataMan, which has been instantiated from a worker thread.

I will keep trying no doubt! :)

[Techno]

OK, correct me if i am wrong but I THINK i got it. here we go:

MainForm:


private string theStatusMessage;
public delegate void TheStatusChanged();
public event TheStatusChanged OnStatusChange;

public IncomingDataManager.TheStatusChanged aDelegate;

//form load event:

this.aDelegate = new namespace.IncomingDataManager.TheStatusChanged(OnStatusChange);
..
..

private void frmMain_OnStatusChange()
{
this.lblCurrentStatus.Text = this.theStatusMessage;
}


Worker thread:


//constructor of Worker Thread Class
this.theDataManager = new IncomingDataManager(someparams);
this.theDataManager.OnStatusChange += this.theMainForm.aDelegate;


IncomingDataMan:

public delegate void TheStatusChanged();
public event TheStatusChanged OnStatusChange;

..
..
//in some method
this.theMainForm.theStatusMessage = "Something";
if (this.OnStatusChange != null)
{
this.OnStatusChange();
}



it seems to work but would like to know if this is ok from the pro's view? :)
how can I be so sure it works? I mean, i have stepped through in the debugger and when the event appears to be raised, it goes into the form and executes the frmMain_OnStatusChange() method! :)

[Techno]

another edit

[Techno]

it does work

wierd thing, tried implementing another event/delegate on another form and it worked but now all of a sudden it doesnt! I get undefined value on the delegate :(

i've even re-written the code but doesnt make a difference. any ideas?

the form:

public delegate void TheNotificationOfDirs();
public event TheNotificationOfDirs OnNotificationOfDirs;
public IncomingDataManager.TheNotificationOfDirs abcDelegate;

..

this.OnNotificationOfDirs += new TheNotificationOfDirs(FrmDirSelector_OnNotificationOfDirs);

//form load:
this.abcDelegate = new [i]namespace[/].IncomingDataManager.TheNotificationOfDirs(OnNotificationOfDirs);


private void FrmDirSelector_OnNotificationOfDirs()
{
MessageBox.Show("Cool!!!");
}


incoming data manager:



public delegate void TheNotificationOfDirs();
public event TheNotificationOfDirs OnNotificationOfDirs;


//constructor:
this.OnNotificationOfDirs += this.theMainForm.theDirSelector.abcDelegate;



.abcdelegate always shows undefined value. But i dont understand, it was working fine a few hours ago and made no change to anything but other code :(