How do you check if the user hasn't made a selection on a combo box?

[RansomHostage]

Just as the title says really! How do you check if the user hasn't made a selection on a combo box? Here's what I've tried, to no avail:

tShirtBuy.addEventListener(MouseEvent.CLICK, sendShirtToCheckout);

function sendShirtToCheckout (evt:MouseEvent):void {
	if (tShirtColour.selectedItem.value == "" || tShirtSize.selectedItem.value == "") {
		trace("worked!")
	} else {
		trace("fail!")
	}
}

which gives the error:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at indoorshredwebsite_fla::shopmc_17/sendShirtToCheckout()

[flosculus]

normally combo boxes in all programs show a default option. you could make the first option a: ' - ' for example.
then the selected index by default would be 0.

then do a check like this:

if(tShirtColour.selectedIndex == 0) {

}

thats how its done in javascript, so it should be the same.

flos

[RansomHostage]

That works marvellously, thanks flosculus.

I just did something slightly different to make it even better. Instead of adding the " - " label, I set the "prompt" value in the component inspector to " - " and used:

if(tShirtColour.selectedIndex == -1) {

}

Thanks once again!