Using the <i class="emphasis">CheckedListBox</i> Class

Using the CheckedListBox Class

As discussed in the In Depth section of this chapter, checked list boxes support checkboxes for each item. The CheckedListBox class is derived from the ListBox class like this (note that that means you can use the ListBox members we've already covered in this chapter in CheckListBox controls):

Object
   MarshalByRefObject
      Component
         Control
            ListControl
               ListBox
                  CheckedListBox

You can find the more notable public properties of the ListBox class in Table 7.4, the more notable methods in Table 7.5, and the more notable events in Table 7.6. Note that as with other Windows controls, I am not listing the notable properties, methods, and events ListBox inherits from the Control class, such as the Click event—you can see all that in Tables 5.1, 5.2, and 5.3 in Chapter 5.

Table 7.4: Noteworthy public properties of *CheckedListBox* objects.
Property	Means
CheckedIndices	Holds the collection of checked indices in this checked list box.
CheckedItems	Holds the collection of checked items in this checked list box.
CheckOnClick	Gets/sets if the checkbox should be toggled when the corresponding item is selected.
ColumnWidth	Gets/sets the width of columns; use this only in multicolumn checked list boxes.
DisplayMember	Indicates which property of object in the list box to show. If empty, the checked list box uses the object's ToString method instead.
HorizontalScrollbar	Gets/sets if a the checked list box should display a horizontal scroll bar.
IntegralHeight	Gets/sets a value specifying if the checked list box should automatically resize so it doesn't partial items.
ItemHeight	Returns the height of an item.
Items	Returns a collection of items in this checked list box.
MultiColumn	Gets/sets if the checked list box allows multiple columns.
ScrollAlwaysVisible	Gets/sets if the checked list box always shows a vertical scroll bar.
SelectedIndex	Gets/sets the index of the selected item in a checked list box.
SelectedIndices	Gets a collection that contains the zero-based indices of all currently selected items in the checked list box.
SelectedItem	Gets/sets the selected item in the checked list box.
SelectedItems	Gets a collection containing the selected items in the checked list box.
SelectionMode	Gets/sets the current selection mode.
Sorted	Gets/sets if the items in the checked list box should be sorted. The sort is alphabetical.
Text	Gets the text of the selected item in a checked list box.
ThreeDCheckBoxes	Gets/sets if the checkboxes are displayed Flat or Normal.
TopIndex	Gets/sets the index of the first item that is visible in the checked list box.

Table 7.5: Noteworthy public methods of *CheckedListBox* objects.
Method	Means
BeginUpdate	Turns off visual updating of the list box until the EndUpdate method is called.
ClearSelected	Unselects all items in a checked list box.
EndUpdate	Resumes visual updating of the checked list box.
FindString	Finds the first item that begins with the indicated string in the checked list box.
FindStringExact	Finds the first item in the checked list box that matches the indicated string exactly.
GetItemChecked	Gets if the indicated item is checked or not.
GetItemCheckState	Gets the check state of the current item.
GetItemHeight	Gets the height of an item in the checked list box.
GetItemText	Gets an item's text.
GetSelected	Gets if the indicated item is selected.
IndexFromPoint	Returns the index of the item at the indicated coordinates.
SetItemChecked	Checks the item at the indicated index.
SetItemCheckState	Sets the indicated item's check state.
SetSelected	Selects or clears the selection for the indicated item in a checked list box.

Table 7.6: Noteworthy public events of *CheckedListBox* objects.
Event	Means
ItemCheck	Occurs when an item's checked state changes.
SelectedIndexChanged	Occurs when the SelectedIndex property has changed.

Here's one property to note in particular— CheckOnClick. When you set this property to True, an item in a checked list box is checked or unchecked when you click it; otherwise, it takes a double-click. I'll set CheckOnClick to True for the CheckedListBoxes example in this chapter. (The default setting for this property is False.)