VB.NET multithreading, callbacks, and passing events to the main thread

Hmm.
I accomplish this by having my threads fire an event.
And I have my main thread be the listener for that event.

Great

Do you have / know of a good example of this? I have not had much luck with one...

Thanks,

Andrew

Hmm.
I accomplish this by having my threads fire an event.
And I have my main thread be the listener for that event.

Well I made a class with a public event say:
public event DoinStuffHandler DoinStuff;

And the delegate would be like:
public delegate int DoinStuffHandler(string somestring, int someint);


Then in my main thread I create an instance of this class and assign the event handler:
myclassthing.DoinStuff+=new DoinStuffHandler(myclassthing_DoinStuff);


Then in my class I can fire the event whenever I want, and my main thread will execute the myclassthing_DoinStuff function.

Plater,

Thanks again for your response... You see, I thought I was doing that too... I thought that using async callbacks implied that the main thread would actually execute the callback event, but according to my thread viewer, the callback is still on the other thread... which explains why my code is blowing up...

To give you some context as to the specific issue, I have a pair of classes that allow my to dynamically monitor a folder and notify the main app if a new item appears in it... The thread's only job is to take the contextual information given during the init, and provide notifications as to the arrival of new items.

Since I wanted to have multiple monitoring, I created a collection class and put my callback delegate subs there, as this collection class is instantiated on the main thread. The delegate subs also funnel all the callbacks from the multiple classes into a single return callback.

So, In practice, it seems to work alright.. like I said before, except that when the callback executes, it is doing so, on the callback thread, not the main thread...

So the relevant code for the collection class:


And the individual class:


I hope you can get the Jist of what I am trying to achieve here...



Thanks again...

Andrew

Well I made a class with a public event say:
public event DoinStuffHandler DoinStuff;

And the delegate would be like:
public delegate int DoinStuffHandler(string somestring, int someint);


Then in my main thread I create an instance of this class and assign the event handler:
myclassthing.DoinStuff+=new DoinStuffHandler(myclassthing_DoinStuff);


Then in my class I can fire the event whenever I want, and my main thread will execute the myclassthing_DoinStuff function.

Isn't there a FileSystemWatcher class or something that does just that?

I think the point of async callbacks are that the event happens on the foreign thread, but does a pass through over into the main thread?

That's what I got out of using a backgroundworker object (msdn told me to when I wanted many threads to be able to update a textbox)

Plater,

Im sure that is the case, but the code is for a workaround for an obtuse email client without a message notification.. So, this (is supposed to) artificially create that..

Anyway, I am open-minded to whatever works... I just hadnt played with that component, mostly because my code has no form on which to put this on.. The application is actually an integration, so I have no main form per se...

So, unless I can somehow extend my class by inheriting the component, I dont see how else it would work...


Andrew

Isn't there a FileSystemWatcher class or something that does just that?

I think the point of async callbacks are that the event happens on the foreign thread, but does a pass through over into the main thread?

That's what I got out of using a backgroundworker object (msdn told me to when I wanted many threads to be able to update a textbox)