The Windows Phone 8 brought in the support for the SD card in the new phones. The Windows Phone 8 SDK allows the developers to read the data from SD card Programatically in Windows Phone 8, but how about this one ?
Can Data be Written Programatically to SD Card in Windows Phone 8?
The Windows Phone 8 SDK currently provides the ExternalStorageAPI which provides the read-only access to the files on SD card. Currently, it does not provides the write access and hence the data cannot be written back to SD card in Windows Phone 8.