---
description: "Learn more about: CSplitButton Class"
title: "CSplitButton Class"
ms.date: "11/19/2018"
f1_keywords: ["CSplitButton", "AFXCMN/CSplitButton", "AFXCMN/CSplitButton::CSplitButton", "AFXCMN/CSplitButton::Create", "AFXCMN/CSplitButton::SetDropDownMenu", "AFXCMN/CSplitButton::OnDropDown"]
helpviewer_keywords: ["CSplitButton [MFC], CSplitButton", "CSplitButton [MFC], Create", "CSplitButton [MFC], SetDropDownMenu", "CSplitButton [MFC], OnDropDown"]
ms.assetid: 6844d0a9-6408-4e44-9b5f-57628ed8bad6
---
# CSplitButton Class
The `CSplitButton` class represents a split button control. The split button control performs a default behavior when a user clicks the main part of the button, and displays a drop-down menu when a user clicks the drop-down arrow of the button.
## Syntax
```
class CSplitButton : public CButton
```
## Members
### Public Constructors
|Name|Description|
|----------|-----------------|
|[CSplitButton::CSplitButton](#csplitbutton)|Constructs a `CSplitButton` object.|
### Public Methods
|Name|Description|
|----------|-----------------|
|[CSplitButton::Create](#create)|Creates a split button control with specified styles and attaches it to the current `CSplitButton` object.|
|[CSplitButton::SetDropDownMenu](#setdropdownmenu)|Sets the drop-down menu that is displayed when a user clicks the drop-down arrow of the current split button control.|
### Protected Methods
|Name|Description|
|----------|-----------------|
|[CSplitButton::OnDropDown](#ondropdown)|Handles the BCN_DROPDOWN notification that the system sends when a user clicks the drop-down arrow of the current split button control.|
## Remarks
The `CSplitButton` class is derived from the [CButton](../../mfc/reference/cbutton-class.md) class. The split button control is a button control whose style is BS_SPLITBUTTON. It displays a custom menu when a user clicks the drop-down arrow. For more information, see the BS_SPLITBUTTON and BS_DEFSPLITBUTTON styles in [Button Styles](/windows/win32/Controls/button-styles).
The following figure depicts a dialog box that contains a pager control and a (1) split button control. The (2) drop-down arrow has already been clicked and the (3) submenu is displayed.
## Inheritance Hierarchy
[CObject](../../mfc/reference/cobject-class.md)
[CCmdTarget](../../mfc/reference/ccmdtarget-class.md)
[CWnd](../../mfc/reference/cwnd-class.md)
[CButton](../../mfc/reference/cbutton-class.md)
`CSplitButton`
## Requirements
**Header:** afxcmn.h
This class is supported in Windows Vista and later.
Additional requirements for this class are described in [Build Requirements for Windows Vista Common Controls](../../mfc/build-requirements-for-windows-vista-common-controls.md).
## CSplitButton::Create
Creates a split button control with specified styles and attaches it to the current `CSplitButton` object.
```
virtual BOOL Create(
DWORD dwStyle,
const RECT& rect,
CWnd* pParentWnd,
UINT nID);
```
### Parameters
*dwStyle*\
[in] A bitwise combination (OR) of styles to be applied to the control. For more information, see [Button Styles](../../mfc/reference/styles-used-by-mfc.md#button-styles).
*rect*\
[in] A reference to a [RECT](/windows/win32/api/windef/ns-windef-rect) structure that contains the position and size of the control.
*pParentWnd*\
[in] A non-null pointer to a [CWnd](../../mfc/reference/cwnd-class.md) object that is the parent window of the control.
*nID*\
[in] The ID of the control.
### Return Value
TRUE if this method is successful; otherwise, FALSE.
## CSplitButton::CSplitButton
Constructs a `CSplitButton` object. The constructor's parameters specify a submenu that is displayed when a user clicks the drop-down arrow of the split button control.
```
CSplitButton();
CSplitButton(
UINT nMenuId,
UINT nSubMenuId)
CSplitButton(CMenu* pMenu)
```
### Parameters
*nMenuId*\
[in] The resource ID of the menu bar.
*nSubMenuId*\
[in] The resource ID of a submenu.
*pMenu*\
[in] A pointer to a [CMenu](../../mfc/reference/cmenu-class.md) object that specifies a submenu. The `CSplitButton` object deletes the `CMenu` object and its associated HMENU when the `CSplitButton` object goes out of scope.
### Remarks
Use the [CSplitButton::Create](#create) method to create a split button control and attach it to the `CSplitButton` object.
## CSplitButton::OnDropDown
Handles the BCN_DROPDOWN notification that the system sends when a user clicks the drop-down arrow of the current split button control.
```
afx_msg void OnDropDown(
NMHDR* pNMHDR,
LRESULT* pResult);
```
### Parameters
*pNMHDR*\
[in] Pointer to an [NMHDR](/windows/win32/api/richedit/ns-richedit-nmhdr) structure that contains information about the [BCN_DROPDOWN](/windows/win32/Controls/bcn-dropdown) notification.
*pResult*\
[out] (Not used; no value is returned.) Return value of the [BCN_DROPDOWN](/windows/win32/Controls/bcn-dropdown) notification.
### Remarks
When the user clicks the drop-down arrow on a split button control, system sends a BCN_DROPDOWN notification message, which the `OnDropDown` method handles. However, the `CSplitButton` object does not forward the BCN_DROPDOWN notification to the control that contains the split button control. Consequently, the containing control cannot support a custom action in response to the notification.
To implement a custom action that the containing control supports, use a [CButton](../../mfc/reference/cbutton-class.md) object with a style of BS_SPLITBUTTON instead of a `CSplitButton` object. Then implement a handler for the BCN_DROPDOWN notification in the `CButton` object. For more information, see [Button Styles](../../mfc/reference/styles-used-by-mfc.md#button-styles).
To implement a custom action that the split button control itself supports, use [message reflection](../../mfc/tn062-message-reflection-for-windows-controls.md). Derive your own class from the `CSplitButton` class and name it, for example, CMySplitButton. Then add the following message map to your application to handle the BCN_DROPDOWN notification:
```
BEGIN_MESSAGE_MAP(CMySplitButton,
CSplitButton)
ON_NOTIFY_REFLECT(BCN_DROPDOWN, &CMySplitButton::OnDropDown)
END_MESSAGE_MAP()
```
## CSplitButton::SetDropDownMenu
Sets the drop-down menu that is displayed when a user clicks the drop-down arrow of the current split button control.
```cpp
void SetDropDownMenu(
UINT nMenuId,
UINT nSubMenuId);
void SetDropDownMenu(CMenu* pMenu);
```
### Parameters
*nMenuId*\
[in] The resource ID of the menu bar.
*nSubMenuId*\
[in] The resource ID of a submenu.
*pMenu*\
[in] Pointer to a [CMenu](../../mfc/reference/cmenu-class.md) object that specifies a submenu. The `CSplitButton` object deletes the `CMenu` object and its associated HMENU when the `CSplitButton` object goes out of scope.
### Remarks
The *nMenuId* parameter identifies a menu bar, which is a horizontal list of menu bar items. The *nSubMenuId* parameter is a zero-based index number that identifies a submenu, which is the drop-down list of menu items associated with each menu bar item. For example, a typical application has a menu that contains the menu bar items, "File," "Edit," and "Help." The "File" menu bar item has a submenu that contains the menu items, "Open," "Close" and "Exit." When the drop-down arrow of the split-button control is clicked, the control displays the specified submenu, not the menu bar.
The following figure depicts a dialog box that contains a pager control and a (1) split button control. The (2) drop-down arrow has already been clicked and the (3) submenu is displayed.
### Example
The first statement in the following code example demonstrates the [CSplitButton::SetDropDownMenu](#setdropdownmenu) method. We created the menu with the Visual Studio resource editor, which automatically named the menu bar ID, IDR_MENU1. The *nSubMenuId* parameter, which is zero, refers to the only submenu of the menu bar.
[!code-cpp[NVC_MFC_CSplitButton_s2#1](../../mfc/reference/codesnippet/cpp/csplitbutton-class_1.cpp)]
## See also
[CSplitButton Class](../../mfc/reference/csplitbutton-class.md)
[Hierarchy Chart](../../mfc/hierarchy-chart.md)
[CButton Class](../../mfc/reference/cbutton-class.md)