Ensuring a listbox has at least one value in it

[Simon]

Hi

Does anyone know how I can be sure that a listbox has a value in it without
doing a post back?

If I attach a required field validator it will only allow the page to submit
if I actually highlight one of the items in the listbox to validate.

I'm really hoping that this can be done somehow using the required field
validator. I've looked at the custom validator control but that looks like
way to much hassle especially seeing as I don't know javascript

Thanks to anyone who can help

Simon

 

[Raterus]

Well you are creating the contents for the listbox from your server-side script right? Can't you check it there? Unless the user is dynamically adding values to this listbox, which if that is the case, you probably created that, and therefore you know just a little about javascript . I don't see how a requiredfieldvalidator would work in this case, if they don't actually have to select a value. You'll have to make your own javascript to check this, shouldn't be too hard.

 

[Vidar Petursson]

Hi,

For multiple you can
var e = document.forms[0].SELECTNAME;
var b = 0;
for(i=0;i<e.length;i++)
{
if(e.options.selected) b++;
}
if(!b) alert("Select something");


First option a no go
if(e.selectedIndex < 1 ) alert("Select something");

More info
http://msdn.microsoft.com/library/d...hor/dhtml/reference/dhtml_reference_entry.asp

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Vidar Petursson
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[Simon Harvey]

Thanks guys

Simon