Re: Threads can't communicate without a while(true) loop? - C# Discussion Boards

Re: Thread Sleeping using an enum

23-Nov-02 5:16

It's still an enum of type RefreshRate. What you need to do is put:

oThread.Sleep((int)RefreshRate.fast);

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Nick Parker24-Nov-02 18:40

Nick Parker

24-Nov-02 18:40

David Stone wrote:
oThread.Sleep((int)RefreshRate.fast);

You don't necessarily need to cast the enum; this should work explicitly when you identify the base type of the enum:

public enum RefreshRate<code> : int</code>
{
fast = 100, 
medium = 500,
slow = 1000
}

oThread.Sleep(RefreshRate.fast);

Nick Parker

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May the roof over your head be always strong.
And may you be in heaven half an hour before the devil knows you’re dead. - Irish Blessing

Re: Thread Sleeping using an enum

David Stone25-Nov-02 8:43

Threads can't communicate without a while(true) loop?

25-Nov-02 8:43

That, and I just noticed that he was doing oThread.Sleep(RefreshRate);

He wasn't specifying a value at all.

Bog22-Nov-02 16:56

Bog

22-Nov-02 16:56

I have a main thread on which GIU Controls all live, and when the user clicks a button, I have a worker thread start doing calculations. While the worker thread does calculations, the main GUI thread is free to let the user click around in the app, look at tab pages, etc..

When the worker is done, I want it to throw an event to tell the main GUI thread that it's finished. As I understand it, this isn't possible.

When the worker thread raises the event, and a class on the main GUI thread is listening for it with an eventhandler, the eventhandler does run. But it doesn't run on the main gui thread. It doesn't run on the worker thread either. It runs on some new third thread. I have the worker thread use BeginInvoke to raise the event.

How do I make a worker thread raise an event on the main gui thread instead of creating a third thread?

"Outside of a dog, a book is Man’s best friend. And inside of a dog, it’s too dark to read."
-Groucho Marx

Re: Threads can't communicate without a while(true) loop?

James T. Johnson22-Nov-02 17:20

Re: Threads can't communicate without a while(true) loop?

22-Nov-02 17:20

Short answer, you don't BeginInvoke will cause it to run on a thread from the ThreadPool; Invoke (or just calling the delegate like any other method) will cause it to run in the same thread (ie the worker thread).

What you do is use the (Begin)Invoke method from the form instance to have it run on the same thread as the GUI.

My preferred way of doing this is to use the handler like you already are but make the [edit]~~form~~ handler[/edit] be responsible for calling Invoke on itself.

theThread.theEvent += new EventHandler(this.ThreadIsDone);
 
....
 
private void ThreadIsDone(object sender, EventArgs e)
{
  // Returns true if not running on the GUI thread
  if( InvokeRequired ) 
  {
    Invoke(
       new EventHandler(this.ThreadIsDone), 
       new object [] { sender, e }
    );
    return;
  }
 
  // Code to run when the Thread is done
}

James

- out of order -

Bog22-Nov-02 18:04

Bog

22-Nov-02 18:04

Thanks this is great, I sort of understand why it will work. The only thing is in my case, the object that I have listening for the event isn't a Form, (or any other Control). When it was instantiated, it was created on the main gui thread where the form and controls are, but it isn't a Control itself. So there's no Invoke() method or InvokeRequired within it. I suppose I could make it a Control if I have to, just to get that method.

Is there like an interface or something I can have the object use so that it will have the Invoke() method?

thanks again

"Outside of a dog, a book is Man’s best friend. And inside of a dog, it’s too dark to read."
-Groucho Marx

Re: Threads can't communicate without a while(true) loop?

James T. Johnson23-Nov-02 7:39

Re: Threads can't communicate without a while(true) loop?

23-Nov-02 7:39

Hmmm, that is a slight problem; but I'm curious if it isn't a GUI component then why does it need to run on the GUI thread? If it modifies a Control's properties or calls a Control's methods then can just use that particular control's InvokeRequired property and Invoke method to do the work.

Bog wrote:
Is there like an interface or something I can have the object use so that it will have the Invoke() method?

None that I know of.

James

- out of order -

Bog23-Nov-02 8:51

Bog

23-Nov-02 8:51

James T. Johnson wrote:
I'm curious if it isn't a GUI component then why does it need to run on the GUI thread?

The object isn't a GUI control, but in it's eventhandler for the "I'm finished" event, it creates some GUI components and adds them to some tabpages on the form. To create and add the GUI components, it needs to be one the same thread as the GIU.

Hey but your solution gave me lots of ideas, I think I can do this, thanks very much James.

btw I found the interface, it's ISynchronizeInvoke.

"Outside of a dog, a book is Man’s best friend. And inside of a dog, it’s too dark to read."
-Groucho Marx

Type-safe indexers when inheriting from IList?

Domenic Denicola22-Nov-02 16:49

Domenic Denicola

22-Nov-02 16:49

I am inheriting my class from IList as suggested earlier as a solution to my DataGrid woes. However, it struck me that I would think that it would be best if the indexer, a required property for inheriting from IList, was type-safe, i.e. returned a MyType instead of a simple object. But when I do this:

public MyType this[int index]
{
	get { return (MyType)this.myArrayList[index]; }
	set { return this.myArrayList[index] = value; }
}
object this[int index]
{
	get { return this.myArrayList[index]; }
	set { return this.myArrayList[index] = value; }
}

it gives me this: Class 'MyIListImplementor' already defines a member called 'this' with the same parameter types.

Yet I know the framework classes seem able to create indexers with non-object return values, yet still inherit from IList. Help?

-Domenic Denicola- [CPUA 0x1337]

“I was born human. But this was an accident of fate—a condition merely of time and place. I believe it's something we have the power to change…”

James T. Johnson22-Nov-02 17:33

22-Nov-02 17:33

It does seem like its impossible, but it isn't (thankfully) Big Grin | :-D

C# (and .NET) supports the ability to specify which methods/properties should be used to implement an interface.

To do so, precede the method/property name with the name of the interface and drop the visibility modifier (because interface methods must always be public).

In your case...

public MyType this[int index] {
  get { return (MyType)this.myArrayList[index]; }
  set { return this.myArrayList[index] = value; }
}

object IList.this[int index] {
  get { return this.myArrayList[index]; }
  set { return this.myArrayList[index] = value; }
}

As an aside, if you're using an ArrayList for the underlying implementation why not inherit from CollectionBase and not have to worry about implementing IList, ICollection, etc. You just need to worry about the typesafe methods for your collection.

James

- out of order -

Domenic Denicola22-Nov-02 18:09

Domenic Denicola

22-Nov-02 18:09

Thank you very much! This works great!

James T. Johnson wrote:
As an aside, if you're using an ArrayList for the underlying implementation why not inherit from CollectionBase and not have to worry about implementing IList, ICollection, etc. You just need to worry about the typesafe methods for your collection.

Right... I knew that... really Blush | :O

Methinks my lack of FCL knowledge has made me do a lot more work than I meant to. Thanks for this as well!

-Domenic Denicola- [CPUA 0x1337]

“I was born human. But this was an accident of fate—a condition merely of time and place. I believe it's something we have the power to change…”

James T. Johnson23-Nov-02 7:46

23-Nov-02 7:46

Domenic [Geekn] wrote:
Methinks my lack of FCL knowledge has made me do a lot more work than I meant to.

You are better off for it though Smile | :)

Now you know that it exists and you also learned how you can implement IList in a strongly-typed collection.

James

- out of order -

leppie23-Nov-02 2:25

leppie

23-Nov-02 2:25

Wow James, you never fail to amaze me Smile | :)

"I dont have a life, I have a program." Also, I won't support any software without the LeppieRules variable.

David Stone23-Nov-02 5:19

23-Nov-02 5:19

Ditto here. My only problem was when he said this:
It does seem like its impossible, but it isn't (thankfully)

He didn't use the emoticon! He should have put the extra dash in there. Seriously James, you're an editor! I am really disappointed. Poke tongue | ;-P

James T. Johnson23-Nov-02 7:41

23-Nov-02 7:41

David Stone wrote:
He should have put the extra dash in there.

Blush | :O

I've gotten too used to Trillian's emoticons, I'll go hang my head in shame now.

James

- out of order -

David Stone23-Nov-02 8:03