The FileDialogPermission controls access to system files based on end user selection within the system file dialog, ensuring that the user has knowledge and authorizes any files accessed by code. Code that does not have file permission can access files explicitly selected by the user via the standard open dialog. Having this permission allows code to get read-only access to file(s) selected by the end user. This allows the program to bring up the File Open dialog. The file that the end user selects is returned as a read-only file handle.
This permission allows code to request file access at run time via the standard file dialogs; when the user selects a file that action gives the code one-time access to the file. File access given via the file dialog is independent of the FileIOPermission. If code has both FileDialogPermission and FileIOPermission for a given file it may either use the file dialog UI or silently open the file such as through File class.