Select Folder
StorageFolder Folder1 = await StorageFolder.GetFolderFromPathAsync("C:\\SomeFolder");
Accessing System Folders
Not all folders are accesible by Universal Windows Apps. To make a folder accesible to a UWP app, you can use FolderPermissions command line tool.
E.g., give UWP apps access to c:\test folder:
FolderPermissions c:\test -e
Note this will work only with native Win32 apis for eg. CreateFile2 and not with WinRT apis like StorageFolder, StorageFile etc.
Feel free to comment if you can add help to this page or point out issues and solutions you have found. I do not provide support on this site, if you need help with a problem head over to stack overflow.