Hi @Cuong Su 

Inside the save button logic first find index of that selected value using "ListIndexOf"  action

Which you can find inside System module. Once you got the index now use "ListRemove" action which removes value using Index/position.

Best

Arun

Hi @Cuong Su , 

I propose this easy solution :

• after saving, just refresh the source of the list (aggregate ?)
• in your aggregate, select out the ones that were already selected 
• you'd probably have to do that anyway if this is a screen you can come back to later for altering the selections

Only in cases where this approach yields performance issues, look at doing it yourself with list manipulations on client side.  

In that case, above reply of @Arun Rajput can help you on your way, but is probably only half of the story : you didn't mention this, but your user might at some point be able to deselect what was previously selected, and you need that thing to re-appear in the dropdown ??  So what are you going to do then, add an item to your list on client side ?  So you know the id but where will the name of that item come from, and where in the order of the list will you put it ?

If I would try to do this on client side (only in extreme cases, doing just a refresh of the dataAction is far far far easier) I would probably 

• have an extra calculated attribute in the aggregate, a boolean called ShowInDropdown
• make my aggregate or data action fill this boolean correctly for current case
• have a local list variable in the screen
• in the OnAfterFetch, copy to the local list only those with ShowInDropdown True
• you can easily do that by doing a Listfilter on the full list, and set the local list to the result of the listfilter
• base the dropdown on the local list
• whenever user selects option
  • do whatever you need to do for saving this, and when succesfull
  • do a ListIndexOf into the aggregate result, and set the boolean to false
• whenever user removes option
  • do whatever you need to do for saving this, and when succesfull
  • do a ListIndexOf into the aggregate result, and set the boolean to true
• at end of Save, copy to the local list only those with ShowInDropdown True

Dorine

Hello Cuong,

If the list is been iterating and and one of the item is getting removed from the same list inside for each then system throws this error.

To avoid that use list local variable on for each and remove the item from that local list  and assign filtered list to another local variable and use that variable in dropdown.

This way you won't get this error.

Updated last post with OML, you will find it in Dropdown screen.

Hope this helps,

Komal