Within a container I use a script task to verify the file

eg.

Dim FileInf As FileInfo

FileInf = New FileInfo(Dts.Variables("User::FullFileName").Value.ToString())

Dts.Variables("User::FileSize").Value = CInt(FileInf.Length)

and then depending on the filesize set a status flag, which I then use a precedence constraint outside of the script to select the component output flow as per diagram.