Proper threading

[Nightm@re]

I have a question about what should and shouldn't be done cross-threads. Essentially I want to know if it is safe to change values created in one thread from another thread. Consider my following code:

public void AddCardToAnimate(Card aCard, int aNewX, int aNewY, bool aFlip)
{
	aCard.SetAnimationValues(aNewX, aNewY, aFlip);

	_cards.Add(aCard);

	if(_cards.Count == 1)
	{
		AnimationDelegate ad = new AnimationDelegate(AnimateCards);

		ad.BeginInvoke(null, ad);
	}
}

private void AnimateCards()
{	
	// While there are still cards to be animated
	while(_cards.Count!=0)
	{
		// Get the first card in the array
		Card animatingCard = (Card)_cards[0];

		// Ensure that the card being animated can be seen
		animatingCard.Visible = true; 

		// Animate the card
		MoveCard(animatingCard);

		// Remove the card from the "to be animated" array
                     _cards.RemoveAt(0);
	}
}

I know it might be confusing to know what's going on, but _cards was created in the main thread and many properties accessed within the MoveCard method were also created in the main thread.

Is this ok? Do I either need to encapsulate all of the properties that are being changed into one thread, or have many delegates?

The program seems to work fine this way...but I just want to know the proper way to go about it, and I'm a bit confused with the whole threading thing.

[Nightm@re]

Ok, I think I am less confused now - but still confused.

I originally thought I had read that you should only access objects in the thread they were created.

Apparantly that isn't correct and by using the Monitor object I can ensure everything runs smoothly...

[Memnoch1207]

The Monitor classes Enter and Exit methods place a lock on the method the thread calls, so the data doesn't get out of sych.
Another option is to use the SyncLock block (VB.NET) or lock (C#).

Example:

SyncLock
   'code here
End SyncLock

C#

lock(this)
{
   code here
}