Common Desktop Environment: Style Guide and Certification Checklist

What is the Method for Attaching?

There are two methods of attachment, through the file selection dialog box that comes up when you choose Add File from the Attachment menu, and through drag and drop from File Manager or another application.

Recommended 

eh: 

Drag and drop should not be the only method for attaching objects. 

Recommended 

el: 

When the user chooses something to attach from the file selection dialog box that is not an attachable item, then the user receives an error message explaining why the chosen item cannot be attached. For example: 

The folder "My.Stuff" cannot be attached because it is a folder. Only documents, applications, and scripts can be attached. 

Recommended 

ej: 

When the user attempts to drop something into the attachment list that is not attachable, then the drop fails and the item is snapped back to its source.