The selection field is the portion of a combo box that displays the currently selected list item. In simple and drop-down combo boxes, the selection field is an edit control and can be used to enter text that is not in the list.
An application can retrieve or set the contents of the selection field and can determine or set the edit selection. The application can also limit the amount of text a user can type in the selection field. When the contents of the selection field change, the system sends notification messages to the parent window or dialog box procedure.
To retrieve the content of the selection field, an application can send the WM_GETTEXT message to the combo box. To set the contents of the selection field of a simple or drop-down combo box, an application can send the WM_SETTEXT message to the combo box.
The edit selection is the range of selected text, if any, in the selection field of a simple or drop-down combo box. An application can determine the starting and ending character positions of the current selection by using the CB_GETEDITSEL message. It can also select characters in the edit selection by using the CB_SETEDITSEL message.
Initially, the amount of text that the user can type into the selection field is limited by the size of the selection field. However, if the combobox has the CBS_AUTOHSCROLL style, the text can continue beyond the size of the selection field. An application can use the CB_LIMITTEXT message to limit the amount of text a user can type into the selection field, regardless of whether the control has the CBS_AUTOHSCROLL style.
When the user edits the content of the selection field, the parent window or dialog box procedure receives notification messages. CBN_EDITUPDATE is sent first, indicating that the text in the selection field has been edited. After the altered text is displayed, the system sends CBN_EDITCHANGE. When the selection field content changes as the result of a list item being selected, these messages are not sent.