"Already exists" error notification

Question

I have a dialog box telling the user to upload new pictures, but if one picture already exists there is a notification telling the user this information and he have to remove it himself. The problem is that all uploaded pictures have a green checking-sign, like so:

This of course has to be improved. There should at least not be a green check-sign if the picture already exists.

But is there a way to prevent the error? I don’t want the user to make the error in the first place, and absolutely not having to correct it himself.

Answer 1

How about the approach in Windows and OS X when copying files/folders?

Validate before the file is uploaded, and give the option to the user what they want to do with duplicates: replace, skip, or rename/keep both.

Windows 8

OS X

Answer 2

In general, in any validation process, the validation should be taken before the action performed. So, you have to check for file existence before uploading process, then cancel the upload for the existing file and notify the uploader.