Chapter 4, Problem 9AW

Program Plan Intro

List boxes:

List box controls help to show the list of items which enables the user to choose an item from the list.

• The user may choose one of the items from the list, causing the item to appear selected at runtime.
• The selected items will be displayed on ListBox control.

Get the items from ListBox control:

The item which is selected by user from ListBox is stored into ListBox’s SelectedItem property.

Steps to determine the selected item in Listbox:

If anyone tries to get the value when ListBox’s SelectedItem is empty, then it will occur with an exception.

• Always ensure that item is selected before reading an item in the SelectedItem. The items stored in ListBox with index value.
• This is done by “SelectedIndex” property.
• The item index is stored into SelectedIndex property.
  • The index is a number to determine the position of Items in ListBox.
  • If first item means index value is “0”, second means “1”, and so on. If there is no item in ListBox, then the index value is set to “-1”.
• The following example code checks whether the SelectedIndex property is “-1” or not.

  if(courseListBox.SelectionIndex != -1)

  {

    selectedProduct = productListBox.SelectedItem.ToString();

  }