Messages from combo boxes are sent as notifications in the form of WM_COMMAND messages. The notification message is stored in the high word of the wParam parameter, and an application can process the following combo box notification messages.
| Notification message | Description |
|---|---|
| CBN_CLOSEUP | Indicates the list in a drop-down combo box or drop-down list box is about to close. |
| CBN_DBLCLK | Indicates the user has double-clicked a list item in a simple combo box. |
| CBN_DROPDOWN | Indicates the list in a drop-down combo box or drop-down list box is about to open. |
| CBN_EDITCHANGE | Indicates the user has changed the text in the edit control of a simple or drop-down combo box. This notification message is sent after the altered text is displayed. |
| CBN_EDITUPDATE | Indicates the user has changed the text in the edit control of a simple or drop-down combo box. This notification message is sent before the altered text is displayed. |
| CBN_ERRSPACE | Indicates the combo box cannot allocate enough memory to carry out a request, such as adding a list item. |
| CBN_KILLFOCUS | Indicates the combo box is about to lose the input focus. |
| CBN_SELCHANGE | Indicates the current selection has changed. |
| CBN_SELENDCANCEL | Indicates that the selection made in the drop down list, while it was dropped down, should be ignored. |
| CBN_SELENDOK | Indicates that the selection made drop down list, while it was dropped down, should be accepted. |
| CBN_SETFOCUS | Indicates the combo box has received the input focus. |