Ajaxify product tag selection in backend

[muratcakir]

No description provided.

[mgesing]

Loading via AJAX is not good here. There is no search field in a multiple tags select2 box. If you type something, the input automatically appears at the first position in the popup list and clicking on it will add it as a new tag. An "Enter" does not (!) apply the entry, but removes it again (not very intuitive). Hard to explain.

Better and easier: just load e.g. a maximum of 5000 product tags instead of all. The user won't want to search in such a long list anyway, but will simply enter missing tags directly. Product tags are stored by IProductTagService.UpdateProductTagsAsync and this method ensures that no duplicate tags are stored anyway.