Dropdowns conditions

Hello, I ask for a way to solution:
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I've correcly configure these dropdown. Now SOTTOGALLERIA dropdown view only the subgalleries of GALLERIA
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I would like add a "conditions": if GALLERIA = NONE, in SOTTOGALLERIA Dropdown I would see ALL subgallery, ELSE I would see the subgallery of GALLERIA selected.
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Where I work to reach the goal?
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If you need I add another screeens.
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Thank You.

Have a look at the dynamic dropdown demo.

I saw demo, can I do also with CC6?

Sure

Sorry, but the DYNAMIC action in CF6 is a SWITCH in CC6?
The list of my subgallery dropdown is a READ DATA, what I take in OPTIONS of dropdown?
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Any suggestion? Thanks

Ok, I've correct thanks this tread https://www.chronoengine.com/forums/posts/t106454/cc6-dynamic-dropdown-for-filtering-table?keywords=dynamic%20dropdown
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I' ask if you can help me to below code:
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switch($this->data('gallery_sel')){
 case '':
   $options = {var:dropdown_search_subgallery_all};
   break;
 default:
   $options = ['N/A' => 'Please select one'];
}
return $options;

What I insert instead the variable?
I tried this without success
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$this->set('dropdown_search_subgallery_all', $this->get('dropdown_search_subgallery_all'));

Can't use shortcodes in PHP. Use the switch, just make sure the left part ("possible values") are actually correct. "Other than None" would be an asterix, like this *

Is blank, where I wrong?
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