MediaLibrary.SavePicture Method (String, Byte)
Capabilities for Windows Phone
If you use this API in your Windows Phone app, you must specify the following capabilities in the app manifest. Otherwise, your app might not work correctly or it might exit unexpectedly.
|ID_CAP_MEDIALIB_PHOTO||Windows Phone 8|
|ID_CAP_MEDIALIB||Windows Phone OS 7.1|
For more info, see App capabilities and hardware requirements for Windows Phone.