Lecture Set 12

1. Lecture Set 12 Sequential Files and Structures Part A – Dialog Boxes, Filters, Directories

2. Objectives • Use the OpenFileDialog, SaveFileDialog, and FolderBrowserDialog controls, which allow the end user to select disk files and folders • Introduction to filters • Using directories to locate and save files

3. The OpenFileDialog and SaveFileDialog Controls • All dialog boxes derive from the CommonDialog class and share similar features • The OpenFileDialog and SaveFileDialog controls are derived from the CommonDialog class • These classes allow the end user to select a file to open or save • The FolderBrowserDialog control also derives from the CommonDialog class • This control allows the end user to select a folder

4. Hierarchical Relationships Among Dialog Classes

5. Members of the OpenFileDialog and SaveFileDialog Classes • The CheckFileExists and CheckPathExists properties control whether the end user can select a file or folder that does not exist • The FileName property contains the filename selected by the end user • The Filter property defines the type of files that will be displayed for selection • The FilterIndex property contains the index of the current filter • The Filter and FilterIndex properties work together

6. Members of the OpenFileDialog and SaveFileDialog Classes (continued) • The InitialDirectory property contains the initial folder where the search for files begins • The OverwritePrompt property applies only to the SaveFileDialog; if True, the end user will be prompted before a file is overwritten • The RestoreDirectory property defines whether the current directory will be restored after the end user selects a file • The ShowDialog method displays the respective dialog box

7. Visual Elements of the Open Dialog Box

8. The FilterProperty (Introduction) • The Filter property restricts the files displayed based on a file extension • A filter consists of • A description • Followed by a vertical bar • Followed by the actual filter • Multiple filters can be connected together • Do not put spaces between the vertical bars

9. The Filter Property (Syntax) • Object.Filter = [description1|filter1|description2|filter2 ...] • description1 contains the description of the filter • filter1 contains the filter itself • The characters '*.' precede the three-character file extension of the filter • Use '*.*' to select all files • Vertical bars separate each description, filter pair

10. The Filter Property (Example) • Set the Filter to three possible filters (*.txt), (*.rtf), and (*.*) • Set the FilterIndex to select the second filter by default ofdMain.Filter = "Text files (*.txt)|*.txt|" "Rich text files (*.rtf)|*.rtf|” "All files (*.*)|*.*“; ofdMain.FilterIndex = 2;

11. Filters(A second example) public void EncryptFile() { OpenFileDialogdialog = newOpenFileDialog(); dialog.Filter= "txt files (*.txt)|*.txt|All files (*.*)|*.*"; dialog.InitialDirectory = @"C:\"; dialog.Title= "Please select an image file to encrypt."; if(dialog.ShowDialog() == DialogResult.OK) { //Encrypt the selected file. I'll do this later. :) } // end if } // end EncryptFile

12. The SaveFileDialogControl • The SaveFileDialog control works the same way as the OpenFileDialog control • Set the OverwritePrompt property to True to prevent the end user from accidentally overwriting files

13. Overwrite Prompt Message

14. Displaying the SaveFileDialog (Example) • Display an instance of the SaveFileDialog control named sfdMain • If the user clicks OK, store the filename in the text box named txtFileName DialogResult result; sfdMain.OverwritePrompt = true; result = sfdMain.ShowDialog(); if (result == Windows.Forms.DialogResult.OK) txtFileName.Text = sfdMain.FileName;

15. The FolderBrowserDialog (Introduction) • Use the FolderBrowserDialog to browse for folders instead of files • Members • The Description property contains the text appearing in the title bar • The RootFolder property contains the topmost folder appearing in the dialog box • The SelectedPath property contains the folder selected by the end user • The ShowDialog method displays the dialog box

16. The FolderBroswerDialog Control

17. Using Windows Defined Directories • Members of the System.Environment class are used to get system directories • The SystemDirectory property gets the Windows system directory • The directory is typically C:\Windows\System • The CurrentDirectory property contains the directory from which the application was run • The GetFolderPath method gets a system special folder

18. Special Folders

19. Reading a Special Folder (Example) • Get the special folder corresponding to the Desktop stringdirectoryString; directoryString= Environment.GetFolderPath( Environment.SpecialFolder.Desktop);

20. Using Application-defined Directories • The Application class contains application defined directories • The StartupPath property contains the directory from which the application was started • The ExecutablePath property contains the startup path and executable filename • The UserAppDataPath and LocalUserAppDataPath properties return application data directories