Find ID of selected item from Listbox

[Danielle]

I'm using two related listboxes to transfer data from one list to another.  In my backend, when I reference Request.Form["lstAssociated"] I can get a list of the id's from the listbox that contains the item I selected to send to the other list, however, I don't see anywhere in the data how I can obtain the ID of just the item I have selected.  We are using Razor forms.

[Georgi]

Hi Danielle,

The selected state is solely visual. We highlight the dom element using CSS.

If I understand correctly, you would like to know which elements moved from one listbox to another. Please correct me if I am wrong.

Is it an option to compare the previous state of the listboxes before the user modified them to the submitted data, hence obtaining the relocated items?

[Danielle]

Yes, I supposed I could, I just assumed there would be an event I could tie into which would contain the information of the item being moved.  If not, I will code something like you have described.

Thanks for your help.

[Georgi]

Hi Danielle,

Another option you have is to store the ids of items that change position in a hidden input and then extract the ids from the payload of the request.

[Danielle]

Thanks Georgi. How would I get those ids of the items that changed position?  Or are you saying to store the original values in a hidden input and then compare them on Submit?

[Georgi]

You could get the id of the element that changed position and store it in a hidden input within the Add/Remove event handlers.

e.g.

// listbox config            
.Events(events => events
                .Add("onAdd")
                .Remove("onRemove")
            )

function onRemove(e) {  // e.items is an array that contains all removed items
  // store the ids of removed items here
}