How can I force user to select n elements in a list box control

[tintin_99]

hi

I have listbox and user can select multi lines but I would like to force the user to always select 4 lines . Could you please let me know hpow can I do it in program

Thanks

[RavensFan]

What do you want to have happen if the user selects less than 4 items? Or more than 4 items?  Pop up a dialog box?

You can check the length of the array of the listbox.  Do it in a while loop and only exit the loop if it is equal to 4.  Pop up a dialog if it is not equal to 4.

[altenbach]

Easiest would be an event structure where you check the size of the listbox array. Set a flag once exactly four items are selected and e.g. enable a button that is disabled for any other number of items.

Typically users need to select one item at a time (e.g. by ctrl-clicking). So constantly throwing dialog boxes at the user would interfere strongly with the user experience. Not recommended).

[altenbach]

Here's a quick example:

 

[mikeporter]

Also, be sure to inform the user of your expectations. Selecting 4 things from a single list is not likely to be something that a person would intuitively understand. Use on-screen instructions or tip strips to tell the user what you want. You could also have a count down indicator showing how many selections there are left to make.

Mike...

[johnsold]

I like the count down indicator idea.

Lynn