The image gallery control is designed only to preview and show details for the images. It does not have CRUD operations implemented. In order to insert/delete/update image you need to implement some external form with these operations, which depends on the selected image from the ImageGallery control.
The other option is to use our RadListView control and add different templates. It supports crud operations and you can define different templates for selected items, insert item, edit item, etc.
For example into the item template you can add only an image and delete button. Examples with crud operations you can find here:
Also you can implement functionality for selecting certain items and then delete all selected images. Example which uses selection can be found here:
Also on the following link you can find example which shows only images into the RadListView control with enabled selection:
I hope this helps.
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