DPAPI encryption not working so well with my.settings

Question

when my.settings.datastorage has nothing in it, this works fine. but after i go through this twice, it gives me an error

total_string = "some string"
My.Settings.datastorage = My.Settings.datastorage & DPAPI.Encrypt(total_string)
My.Settings.Save()
MsgBox(DPAPI.Decrypt(My.Settings.datastorage))

this is the error it gives:

"Invalid character in a Base-64 string."

Answer 1

You can't simply concatenate encrypted strings with &, not if you want to decode them later anyway. In order to Add information you'll have to decode what you've already got, combine the clear text en encode the total.