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

Using the ComboBox Class

As discussed in the In Depth section of this chapter, combo boxes combine a text box and a list box (which is why they're called combo boxes). In fact, combo boxes are derived from the ListBox class:

Object
   MarshalByRefObject
      Component
         Control
            ListControl
               ComboBox

You can find the more notable public properties of the ComboBox class in Table 7.7, the more notable methods in Table 7.8, and the more notable events in Table 7.9. Note that as with other Windows forms controls, I am not listing the notable properties, methods, and events ComboBox inherits from the Control class, such as the Click event—you can see all that in Chapter 5, Tables 5.1, 5.2, and 5.3.

Table 7.7: Noteworthy public properties of *ComboBox* objects.
Property	Means
DisplayMember	Indicates which property of the objects in the combo box to show. If empty, the combo box uses the ToString method.
DropDownStyle	Gets/sets the style of the combo box.
DropDownWidth	Gets/sets a combo box's drop-down part's width.
DroppedDown	Gets/sets if the combo box is displaying its drop-down part.
Focused	Gets a value specifying if the combo box has the focus.
IntegralHeight	Gets/sets if the combo box should resize so it doesn't show partial items.
ItemHeight	Gets the height of an item in a combo box.
Items	Gets a collection of the items in this combo box.
MaxDropDownItems	Gets/sets the maximum number of items visible in the drop-down part of a combo box.
MaxLength	Gets/sets the maximum number of characters in the combo box's text box.
SelectedIndex	Gets/sets the index of the currently selected item.
SelectedItem	Gets/sets currently selected item in the combo box.
SelectedText	Gets/sets the selected text in the text box part of a combo box.
SelectionLength	Gets/sets the number of characters selected in the text box part of the combo box.
SelectionStart	Gets/sets the beginning index of selected text in the combo box.
Sorted	Gets/sets if the items in the combo box are sorted.

Table 7.8: Noteworthy public methods of *ComboBox* objects.
Method	Means
BeginUpdate	Turns off visual updating of the combo box until the EndUpdate method is called.
EndUpdate	Resumes visual updating of the combo box.
FindString	Finds the first item in the combo box that begins with the indicated string.
FindStringExact	Finds the item that matches the indicated string exactly.
GetItemText	Gets an item's text.
Select	Selects a range of text.
SelectAll	Selects all the text in the text box of the combo box.

Table 7.9: Noteworthy public events of *ComboBox* objects.
Event	Means
DropDown	Occurs when the drop-down portion of a combo box is shown.
DropDownStyleChanged	Occurs when the DropDownStyle property has changed.
SelectedIndexChanged	Occurs when the SelectedIndex property has changed.