Most Recently Used List in a Combobox


MFC implements a convenient feature called a most recently used list, or MRU. In SDI and MDI apps generated by AppWizard, the MRU list appears on the File menu. However, another handy place where MRUs are used is in comboboxes. For example, the Start/Run dialog lists the last few programs that you've run in its combobox.

While MFC does not directly support placing an MRU in a combobox, the class CRecentFileList (which implements the File menu MRU list) provides several member functions for maintining, saving, and loading an MRU list. My CMRUComboBox class encapsulates this functionality, and adds the logic necessary to put the MRU in a combobox.

CMRUComboBox was written with MSVC 5.0 and MFC 4.2 Although I have not personally tested it in a Unicode app, it should compile and run with no problems, since the code uses CStrings and LPCTSTRs.

Using an MRU combobox

To use CMRUComboBox, create a combobox control with the CBS_DROPDOWN style. Including CBS_AUTOHSCROLL also is not a bad idea. Use ClassWizard to add a member variable of type CComboBox that is hooked to a combobox control. Then, go to the source and change the type of the variable to CMRUComboBox. CMRUComboBox derives from CComboBox so all the operations you normally do with CComboBoxes will still work the same; CMRUComboBox just adds new methods for managing the MRU list.

In your OnInitDialog() (or other initialization code), you will need to set up a few parameters and flags for the MRU list. At minimum, set the maximum size for the MRU list, and the location in the registry (or INI file) where the list will be saved. There are also a few flags you can optionally set, which are described in the HTML documentation that is in the ZIP file that contains the source code.

Once all that initialization is done, call LoadMRU() to read in the saved contents of the MRU list. When you want to add a string to the list, call AddToMRU(). Duplicate strings are automatically brought to the top of the list, just as in File menu MRU lists. When you want to save the contents of the MRU, call SaveMRU().

Methods List

This is a list of all the new methods available for maintaining an MRU. The full docs are included in the ZIP file that contains the source code files.

BOOL            AddToMRU ( LPCTSTR szNewItem )
void            EmptyMRU()
int             SetMaxMRUSize ( int nMaxSize )
int             GetMaxMRUSize()
void            SetMRURegKey ( LPCTSTR szRegKey )
const CString&  GetMRURegKey()
BOOL            SetMRUValueFormat ( LPCTSTR szValueFormat )
const CString&  GetMRUValueFormat()
BOOL            LoadMRU()
BOOL            SaveMRU()
void            RefreshCtrl()
BOOL            SetAutoRefreshAfterAdd ( BOOL bAutoSave )
BOOL            SetAutoSaveAfterAdd ( BOOL bAutoSave )
BOOL            SetAutoSaveOnDestroy ( BOOL bAutoSave )

Simple example

Here is a sample usage of CMRUComboBox. Suppose you have a Find dialog and you want to list the last few search strings (similar to how MSVC does it). Once you've created a CMRUComboBox member variable in your dialog class as described above, you would do the following in your OnInitDialog() function:

    m_combo.SetMRURegKey ( _T("Find Dlg MRU") );
    m_combo.SetMRUValueFormat ( _T("String%d") );
    m_combo.SetMaxMRUSize ( 12 );
    VERIFY ( m_combo.LoadMRU() );

Then, whenever you want to add a string to the MRU, call

    m_combo.AddToMRU ( szSearchString );

Download demo project - 21KB

Download source and docs - 8KB