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Chapter 14

Chapter 14. Additional Topics in C#. Chapter Objectives - 1. Validate user input in the Validating event handler and display messages using an ErrorProvider component Capture and check an individual keystroke from the user Use code snippets in the editor

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Chapter 14

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  1. Chapter 14 Additional Topics in C#

  2. Chapter Objectives - 1 • Validate user input in the Validating event handler and display messages using an ErrorProvider component • Capture and check an individual keystroke from the user • Use code snippets in the editor • Create a multiple-document project with parent and child forms • Arrange child forms vertically, horizontally, or cascaded

  3. Chapter Objectives - 2 • Add toolbars and status bars to your forms using tool strip and status strip controls • Use calendar controls and date methods • Display a Web page on a Windows form using a WebBrowser control • Use WPF Interoperability to add Windows Presentation Framework controls to a Windows Form • Create a WPF application

  4. Advanced Validation Techniques • Using ErrorProvider components • Similar to Web validation controls • Other useful techniques • Set MaxLength and/or CharacterCasing properties of text boxes • Perform field-level validation using the Validating event of input controls

  5. Using ErrorProvider Components - 1 • An ErrorProvider component causes an error messageto appear next to the fieldin error on the form, rather than messages in messageboxes • If the input value is invalid,a blinking icon displaysnext to the field in errorand displays a messagein a popup, similar to aToolTip

  6. Using ErrorProvider Components - 2 • Generally, one ErrorProvider component can be used to validate all controls on the form • It is added to the Component Tray

  7. Using ErrorProvider Components - 3 • Logic same as for a MessageBox solution • Identify an error • Use the Error Provider SetError method • Pops up the icon • General Form • Examples ErrorProviderObject.SetError(ControlName, MessageString); errorProvider1.SetError(quantityTextBox, "Quantity must be numeric."); errorProvider1.SetError(creditCardTextBox, "Required field.");

  8. The MaxLength andCharacterCasing Properties • Help the user enter correct input data in text boxes • MaxLength property • User unable to enter morecharacters than the maximum • CharacterCasing property • Each character user enters is automatically converted to the case specified • Normal (default) • Upper • Lower Input limited to two characters and converted to uppercase

  9. Field-Level Validation • Instead of validating all controls on a form when the user clicks a button, perform field-level validation • Validating event • CausesValidation property • Error Provider components • Error message appears as soon as the user attempts to leave a field with invalid data

  10. Using the Validating Event andCausesValidation Property - 1 • Validating event is best location for validation code • Use CancelEventArgs argument to cancel the event and return focus to the control being validated • Each control on a form has a CausesValidation property, set to true by default • When the focus passes from one control to the next, the CausesValidation property of the new control determines whether the Validating event occurs for the control just left • Set CausesValidation to false on a control such as Cancel or Exit to give the user a way to bypass the validation

  11. Using the Validating Event andCausesValidation Property - 2 • Set the Cancel property of the e argument to true to cancel the Validating event and keep the focus in the field in error private void nameTextBox_Validating(object sender, CancelEventArgs e) { // Validate for a required entry. // Clear any previous error. errorProvider1.SetError(nameTextBox, ""); // Check for an empty string. if (nameTextBox.Text == String.Empty) { // Cancel the event. e.Cancel = true; errorProvider1.SetError(nameTextBox, "Required Field"); } }

  12. Using the Validating Event andCausesValidation Property - 3 • If a validating event requires an entry in the field that receives focus when the form is first displayed, user will be unable to close the form without making an entry • Set e.Cancel = false in the form’s FormClosing event handler Private void ValidationForm_FormClosing(object sender, FormClosingEventArgs e) { //Do not allow validation to cancel the form’s closing. e.Cancel = false; }

  13. Capturing Keystrokesfrom the User - 1 • Check each keystroke that the user enters in the control's KeyDown, KeyPress, or KeyUp event handler • These events occur in the order listed for most keyboard keys • Keystrokes that ordinarily cause an action to occur, such as the Tab key or Enter key generate only a KeyUp event

  14. Capturing Keystrokesfrom the User - 2 • The e argument of the KeyPress event handler is KeyPressEventArgs • KeyChar property holds the character pressed (as a char data type) • To make comparisons, use methods of the char class • Single characters must be enclosed in single quotes • Handled property can be set to true • Indicates that the keystroke needs no further processing • Effectively "throws away" the keystroke

  15. Using the MaskedText Box for Validation • Set the Mask property of a masked text box to help the user enter data in the correct format • Set the Mask property to one of the predefined masks • Write your own • Easiest way—modify one of the existing masks • Follow the syntax rules of a regular expression • Predefined masks include date, time, phone number, Social Security number, and Zip code formats • If the user enters invalid data for the mask, the character is not accepted

  16. Code Snippets • Small samples of code that show how to accomplish many programming tasks • Right-click in the Code Editor and select Insert Snippet • Snippet categories include • loops, decisions, exception handling, and arrays

  17. Sample Projects • Visual Studio includes many sample projects that you can use to learn new techniques • All editions except the Express Edition • Select Help/Contents • Expand the nodes for Development ToolsandLanguages/Visual Studio/Visual C# to find the Visual C# Samples node • Filter for C# • Walkthroughs in Help are another way to learn • Tutorials that give a step-by-step introduction to many techniques and controls

  18. Multiple Document Interface - 1 • SDI – Single document interface • Each form in the project acts independently from the other forms • MDI – Multiple document interface • A parent form and child forms • Example: MS Word has a parent form (the main window) and child forms (each document window) • Open multiple child windows and maximize, minimize, restore, or close each child window • Always stays within boundaries of parent • Close parent window, all child windows close

  19. Multiple Document Interface - 2 • Rules for MDI • If a parent form closes, all children leave with it • Child form always appears inside the parent’s area • C# allows both MDI and SDI (such as a splash form) in the same project • A Window menu displays a list of open windows • Allows the user to move from one active document to another

  20. Multiple Document Interface - 3

  21. Creating an MDI Project - 1 • At design time designate a form as a parent • IsMdiContainer property = true • Designate child forms at run time • Declare a new variable for the form and instantiate it • Set the child’s MdiParent property to the current (parent) form and show it private void childOneToolStripMenuItem_Click(object sender, EventArgs e) { // Display child one form. ChildForm childOneForm = new ChildForm(); childOneForm.MdiParent = this; childOneForm.Show(); }

  22. Creating an MDI Project - 2 • If multiple child windows are displayed, the title bar of each child should be unique • Accomplish by appending a number to the title bar before displaying the form • Similar to Word's Document1, Document2 ChildForm childOneForm = new ChildForm(); childOneForm.MdiParent = this; childOneCountInteger++; childOneForm.Text = "Child One Document " + childOneCountInteger.ToString(); childOneForm.Show();

  23. Adding a Window Menu • Parent form should include a Window menu • Lists open child windows • Allows the user to switch between windowsand arrange multiple child windows • Set the MenuStrip's MdiWindowListItemproperty to the name of the menu to useas the Window menu • Include a separator bar at the bottomof the Window menu • Separates open window list from othermenu choices

  24. Layout Options • Child windows may be arranged in different layouts • Tiled vertically, tiled horizontally, or cascaded • Layout set in code with LayoutMdi method argument • Use one of three constants – TileHorizontal, TileVertical, or Cascade private void tileHorizontallyToolStripMenuItem_Click(object sender, EventArgs e) { // Arrange the child forms horizontally. LayoutMdi(MdiLayout.TileHorizontal); }

  25. Toolbars • Create by using the ToolStrip control • A container that does not yet contain any objects • Several types of objects can be added • ToolStripButtons • ToolStripLabels • Other objects

  26. Setting Up the Buttons - 1 • Add buttons to a tool strip using the drop-down list of objects • Click on Button • Adds a new ToolStripButton object to the ToolStrip • Set the Name and ToolTipText properties • Name the button • i.e. aboutToolStripButton • Assign an image to the Image property

  27. Setting Up the Buttons - 2 • Set button’s AutoSize property to false to make the image display properly • Change DisplayStyle property to Text and modify Text property to display words on the button • Click Insert Standard Items from the ToolStrips’s smart tag or properties window • New, Open, Save, Print, Cut, Copy, Paste and Help Buttons available with pictures • Must create code for each button (not automatic)

  28. Coding for the ToolStrip Buttons • Can create a new event handler for the button click • Since they are shortcuts for menu items, set ToolStripButton’s Click event to the corresponding menu item’s event-handling method

  29. Status Bars • A status bar generally appears across the bottom of a form • Displays information such as date, time, status of Caps Lock and Num Lock keys or error or informational messages • Add a StatusStrip control to the form • Add ToolStripStatusLabel objects to the StatusStrip • Set properties such as Name and ToolTipText at design or run time • Make labels appear at right end of status bar by setting the StatusStrip’s RightToLeft property to true

  30. Displaying the Date and Time - 1 • Use properties and methods of DateTime structure to retrieve and format current date and time • Now property holds system date and time in numeric format • Can be used for calculations • Format date and/or time for display using methods • ToShortDateString, ToLongDateString, ToShortTimeString, ToLongTimeString • Display does not update automatically • Use a Timer component to update the time

  31. Displaying the Date and Time - 2 • Code to update the time on the status strip • Be sure to set the Enabled and Interval properties of the timer private void timer1_Tick(object sender, EventArgs e) { // Update the time on the status strip. // Interval = 1000 milliseconds (one second). timeToolStripStatusLabel.Text = DateTime.Now.ToLongTimeString(); }

  32. The Calendar Controls - 1 • DateTimePicker and MonthCalendar controls display calendars on a form • DateTimePicker takes less screen space • Displays only day and date unless user drops down the calendar • Value property contains date • Control initially displays current date • User selects a date and the program retrieves the Value property • Assign a Date value to the property

  33. The Calendar Controls - 2 Displays a calendar Displays only the day and date unless the user drops down the calendar. Saves screen space.

  34. Displaying Web Pageson a Windows Form • Add a WebBrowser control to a Windows form • Form resembles a browser window in Internet Explorer or displays any HTML page, online or offline • Must have an active Internet connection to display Web pages in the WebBrowser control

  35. The WebBrowser Control • By default control is set to fill entire form (Dock = Fill) • Can add a ToolStrip control for navigation

  36. Checking for the Enter Key • Test if a keystroke is the Enter key in the KeyUp event • The e argument of the KeyUp event handler is KeyEventArgs • KeyCode property holds the key code of the key • Enter key is 13 • Check for the Enter key with either statement if (e.KeyCode == 13) or if (e.KeyCode == Keys.Enter

  37. XML Data Files • Many advantages over other file formats • Platform-independent, not tied to a specific language or vendor • Text-based, can view and edit file with text-edit tools • Easy to make changes • Uni-code compliant and used internationally

  38. Nodes, Elements, and Attributes • Tags delineate elements of the file • Basic structure is a tree • Root node (a file has only one) • Child nodes (can also contain more child nodes) • Nodes at same level referred to as siblings • Within a node values are assigned to attributes

  39. XML File Terminology

  40. Elements in an XML Document

  41. Writing and Reading an XML File • Write an XML file from a program using an XmlWriter object • Contains many methods • Writes properly formed XML files • Elements and attributes identified by tags

  42. C# Tools for Reading XML Files • Use the Load method of an XDocument to read an XML file • Specify a complete path or a URI for the Filename (default is bin\Debug) • Visual Studio’s type inference determines and assigns a strong data type

  43. Loading an XML File intoan XElement Object • Load an XML file into an XElement object • Root node is first item in an XElement object XElement bookData = XElement.Load(“books.xml”); • An XDocument contains information about the document from the top of the file

  44. Using LINQ to XML to Queryan XElement Object • Use LINQ to XML to retrieve data elements from an XElement or XDocument object • Refer to elements in the XElement object on the In clause of LINQ and in the Select clause • Use orderby for sorting and where for conditions • Use a foreach statement to refer to individual attributes of a query, or manipulate the output

  45. Windows PresentationFoundation (WPF) - 1 • WPF provides ability to create richer user interfaces for multiple platform development • Windows Vista uses WPF to bring better multimedia to the operating system • WPF is available in Visual Studio and Microsoft Expression Studio • Microsoft Silverlight is a scaled-down version of WPF • Rich Web-based interface, works with all leading browsers and on multiple platforms • Able to integrate vector-based graphics, media, text, animation and overlays into the Web interface

  46. Windows PresentationFoundation (WPF) - 2 • Web pages are created in two parts, the interface and the application code • Designer creates the interface • Developer does the programming • Expression blend facilitates creating the two parts • In Visual Studio templates exist for a WPF application and for WPF Browser Applications

  47. Windows PresentationFoundation (WPF) - 3 • WPF user interfaces use XAML (Extensible Application Markup Language) • Much more interactive than traditional HTML • XBAP refers to a XAML Browser Application • Runs in an Internet browser • Technology allows creation of hybrid applications

  48. WPF Interoperability - 1 • Allows use of WPF controls in a Windows Forms application • ElementHost available by default • A container that allows addition of other WPF controls to the Windows Form • Add additional available controls at run time, rather than design time • To use WPF Interoperability, add the ElementHost control to a Windows Form • Add the WPF controls in code • Include a using statement for System.Windows.Controls

  49. WPF Interoperability - 2 • Expander control allows part of a page to show or be hidden • User clicks to expand the control, value of the Content property displays

  50. Writing a WPF Application • IDE layout for a WPF application resembles ASP.NET layout • Document window is split, shows XAML and the design • Collapse the XAML screen • Use the grid container to help with flow layout and to place controls • Grid lines can be set to desired height and width • Many controls have same function and feel as Windows Forms controls • Extra properties available with WPF controls

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