Question:
i have a dropdownlist (asp.net control) and a listbox control and a Add button when the user select the item from dropdownlist and click on add button to add to the listbox.
how can i prevent the user from adding duplciate items and alert saying its already in the listbox?
UPDATE:
in my particular scenario, i have a dropdwonlist and adding the item to listbox both are asp.net controls and i am adding the items from code-behind and your solution is pure on client side, is there a way i can read the listbox and compare and alert the message?
Solution:1
Pretty easy. With this simple markup:
<select id="items"> <option>One</option> <option>Two</option> <option>Three</option> </select> <input type="button" id="add" value="Add" /> <select id="result" multiple="multiple" size="5"> </select> This would be the jQuery:
$('#add').click(function(){ var item = $('#items').val(); var $result = $('#result>option[value="' + item + '"]'); if($result.length == 0){ $('#result').append('<option value="' + item + '">' + item + '</option>'); } else{ alert('The item "' + item + '" has already been added'); } }); Check the fiddle: http://jsfiddle.net/mKFzz/
Edit: If you want to do it as per @ryangavin's suggestion, here is the fiddle: http://jsfiddle.net/baLZN/
Solution:2
One way is to remove the item form the dropdownlist after it's added, that way the user can't even select it a second time. Removes the need for annoying alerts.
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