ListBox Control Objects - Displaying, Adding, and Selecting Items

2. Chapter 9 Programming Based on Events Microsoft Visual C# .NET: From Problem Analysis to Program Design

3. ListBox Control Objects • Displays list of items for single or multiple selections • Scroll bar is automatically added when total number of items exceeds the number that can be displayed • Can add or remove items at design time or dynamically at runtime • Includes number of properties and events • Items property used to set initial values • Click on (Collections) to add items

4. Adding a ListBox Control Object Add ListBox control, then click on Items property (Collection) to type entries

5. ListBox Control Objects (continued) • Name property • Useful to set for program statements • Sorted property • Set to true to avoid having to type values in sorted order • Register an event for the ListBox • Might want to know when the item selection changes • Double-clicking on any control registers its default event for the control • SelectedIndexChanged—default event for ListBox

6. ListBox Control Objects (continued) • Register its event with the System.EventHandler delegate this.lstBoxEvents.SelectedIndexChanged += new System.EventHandler (this.listBox1_SelectedIndexChanged); • Visual Studio .NET adds event handler method private void listBox1_SelectedIndexChanged (object sender, System.EventArgs e) { }

7. ListBox Control Objects (continued) • To retrieve string data from ListBox use Text property this.txtBoxResult.Text = this.lstBoxEvents.Text; • Place in method body • When event fires, selection retrieved and stored in TextBox object

8. ListBox Control Objects (continued)

9. Multiple Selections with a ListBox • SelectionMode Property has values of MultiSimple, MultiExtended, None and One • MultiSimple: use the spacebar and click of mouse • MultiExtended can also use Ctrl key, Shift key, and arrow keys foreach(string activity in lstBoxEvents.SelectedItems) { result += activity + " "; } this.txtBoxResult.Text = result;

10. ListBox Control Objects (continued)

11. ListBox Control Objects (continued) • SelectedItem and SelectedItems returns objects • Store numbers in the ListBox, once retrieved as objects, cast the object into an int or double for processing • Adding items to a ListBox at runtime by using Add( ) method with the Items property lstBoxEvents.Items.Add("string value to add"); privatevoid btnNew_Click(object sender, System.EventArgs e) { lstBoxEvents.Items.Add(txtBoxNewAct.Text); }

12. ListBoxExample

13. ListBoxExample—Properties Set

14. ListBoxExample—Properties Set (continued)

15. Properties of the ListBox Class

16. Methods of the ListBox Class Remember ListBox object also inherits members from Control class

17. ListBoxExample—Properties Set (continued)

18. Properties of the ListBox Class

19. Methods of the ListBox Class Remember ListBox object also inherits members from Control class