ComboBox Class

Object
  VObject
    Control
      TextControl
        BaseListBox
          ListBox
            ComboBox
              ComboBoxEx

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A combo box (also known as a combination box) is a control that combines the abilities of an edit control and a list box. There are three types of combo boxes—simple, drop-down, and drop-down list. A combo box displays a list of items or choices to the user, as well as allowing text to be entered directly into an edit area. The combo box methods will allow you to add, arrange, remove, and interrogate the list of items. When one of the items is selected, ComboBox:CurrentItem, ComboBox:CurrentItemNo, ComboBox:TextValue, and ComboBox:Value are updated. Either a one-dimensional or two-dimensional array is specified in the FillUsing() method, with a row for each of the items available for selection. With a two-dimensional array, the first element is called the display value, and the second element is called the return value. When an item is selected, the ComboBox:TextValue contains the first element (the display value), and ComboBox:Value contains the second element (the return value). When text is directly entered, ComboBox:CurrentItemNo is set to 0 and the new text is stored in ComboBox:TextValue and ComboBox:Value. A combo box may be bound to a field (character, date, logical, numeric, or memo) in a server. The field's data value is stored in ComboBox:Value. The combo box compares the data value to the second element values specified in the FillUsing() array, and if a match is found, the first element (the display value) is stored in ComboBox:TextValue. In a "no-match" situation, the combo box shows no item selected, ComboBox:CurrentItem is NULL_STRING, ComboBox:CurrentItemNo is set to 0, and ComboBox:TextValue and ComboBox:Value reflect the field contents. If an item is selected, ComboBox:CurrentItemNo is set to a number between 1 and ComboBox:ItemCount, and the corresponding second element is stored as ComboBox:Value and as the field's data value. If text is directly entered, it will also be stored as the field's data value. Use the Window:ListBoxSelect() event handler to respond to selections, and the Window:ListBoxClick() event handler to respond to choices. A combo box is primarily a selection device, so there is no special support for the functionality available in the Edit class. However, the contents of the edit component can be changed or obtained using the inherited CurrentText access/assign methods. The combo box also generates EditFocusChangeEvents when its edit control loses or receives the focus.

This example creates a combo box and fills it with a list of animals: This example creates a combo box with different currencies, showing an explicit representation to the user but using a different representation internally: This example creates a combo box that shows the products available in the product table: