Microsoft KB Archive/253171

= How To Create a Most Recently Used (MRU) File List in Visual Basic =

Article ID: 253171

Article Last Modified on 7/14/2004

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APPLIES TO


 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 6.0 Learning Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition
 * Microsoft Visual Basic 4.0 Standard Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 16-bit Enterprise Edition
 * Microsoft Visual Basic 4.0 32-Bit Enterprise Edition

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This article was previously published under Q253171



SUMMARY
Many applications offer a list of most recently used files (usually referred to as an MRU list and located on the File menu). This MRU list allows for quick selection of a file or project that was recently opened without having to select FILE-OPEN and browse or search to locate that file. This article demonstrates one approach to achieving this functionality.



MORE INFORMATION
Visual Basic does not provide any built-in mechanism for managing a list of recently used files. However, as a developer, you can easily create this list through the use of a menu control array. The use of a menu control array allows you to dynamically add menu items to a Visual Basic form during program execution. There are some prerequisites for a menu control array to work. Primarily, the first element of the array must be created during the development of the application. This is as simple as creating the menu item as usual and then setting its INDEX property to the numeric value of 0, thus making this menu item the first element, element 0, of the array. Once this is done, the LOAD method can be used to create additional elements in that array. One important thing to note is that, by default, the VISIBLE property of control array elements created at run time is FALSE. Therefore, you also need to set this property if you want the user to see the new item.

For more information on menu control arrays and control arrays in general, please refer to Visual Basic's Online documentation by searching for "Control Array."

Following are steps to create a small fully functioning example application featuring an MRU file list. This example demonstrates the following features:
 * It is dynamic and supports a various number of MRU items.
 * A maximum number of MRU entries can be defined.
 * The list is always sorted from the "most recent" to "least recent."
 * The MRU list is saved to the registry upon application termination and loaded upon application startup.

STEPS TO CREATE SAMPLE
 Create a new Visual Basic Standard EXE project. Form1 is created by default. From the Project menu, select Components, check Microsoft Common Dialog control, and click OK. Add a Common Dialog control to Form1.  From the Tools menu, select Menu Editor, and create the following menu structure:    File (Name = mnuFile) ---Open (Name = mnuOpen) ---MRU FileList (Name = mnuMRU, Visible = False, Index = 0) ---Quit (Name = mnuQuit)   Paste the following code into Form1's code window: Option Explicit

Private Const MaxMRU = 4 'Maximum number of MRUs in list (-1 for no limit) Private Const NotFound = -1  'Indicates a duplicate entry was not found Private Const NoMRUs = -1    'Indicates no MRUs are currently defined

Private MRUCount As Long     'Maintains a count of MRUs defined

Private Sub Form_Load ' Initialize the count of MRUs MRUCount = NoMRUs ' Call sub to retrieve the MRU filenames GetMRUFileList End Sub

Private Sub Form_Unload(Cancel As Integer) ' Call sub to save the MRU filenames SaveMRUFileList End Sub

Private Sub mnuMRU_Click(Index As Integer) ' Call sub to reorder the MRU list ReorderMRUList mnuMRU(Index).Caption, CLng(Index) End Sub

Private Sub mnuOpen_Click ' Show the file open common dialog Me.CommonDialog1.ShowOpen ' Call sub to add this file as an MRU AddMRUItem Me.CommonDialog1.FileName End Sub

Private Sub AddMRUItem(NewItem As String) Dim result As Long ' Call sub to check for duplicates result = CheckForDuplicateMRU(NewItem) ' Handle case if duplicate found If result <> NotFound Then ' Call sub to reorder MRU list ReorderMRUList NewItem, result Else ' Call sub to add new item to MRU menu AddMenuElement NewItem End If End Sub

Private Function CheckForDuplicateMRU(ByVal NewItem As String) As Long Dim i As Long ' Uppercase newitem for string comparisons NewItem = UCase$(NewItem) ' Check all existing MRUs for duplicate For i = 0 To MRUCount If UCase$(Me.mnuMRU(i).Caption) = NewItem Then ' Duplicate found, return the location of the duplicate CheckForDuplicateMRU = i        ' Stop searching Exit Function End If  Next i   ' No duplicate found, so return -1 CheckForDuplicateMRU = -1 End Function

Private Sub mnuQuit_Click ' Close the program Unload Me End Sub

Private Sub AddMenuElement(NewItem As String) Dim i As Long ' Check that we will not exceed maximum MRUs If (MRUCount < (MaxMRU - 1)) Or (MaxMRU = -1) Then 'Increment the menu count MRUCount = MRUCount + 1 ' Check if this is the first item If MRUCount <> 0 Then ' Add a new element to the menu Load mnuMRU(MRUCount) End If     ' Make new element visible mnuMRU(MRUCount).Visible = True End If  ' Shift items to maintain most recent to least recent For i = (MRUCount) To 1 Step -1 ' Set the captions mnuMRU(i).Caption = mnuMRU(i - 1).Caption Next i  ' Set caption for new item mnuMRU(0).Caption = NewItem End Sub

Private Sub ReorderMRUList(DuplicateMRU As String, DuplicateLocation As Long) Dim i As Long ' Move entries previously "more recent" than the ' duplicate down one in the MRU list For i = DuplicateLocation To 1 Step -1 mnuMRU(i).Caption = mnuMRU(i - 1).Caption Next i  ' Set caption of newitem mnuMRU(0).Caption = DuplicateMRU End Sub

Private Sub GetMRUFileList Dim i As Long          'Loop control variable Dim result As String   'Name of MRU from registry ' Loop through all entries Do     ' Retrieve entry from registry result = GetSetting(App.Title, "MRUFiles", Trim$(CStr(i)), "") ' Check if a value was returned If result <> "" Then ' Call sub to additem to MRU list AddMRUItem result End If     ' Increment counter i = i + 1 Loop Until (result = "") End Sub

Private Sub SaveMRUFileList Dim i As Long          ' Loop control variable ' Loop through all MRU For i = 0 To MRUCount ' Write MRU to registry with key as it's position in list SaveSetting App.Title, "MRUFiles", Trim$(CStr(i)), mnuMRU(i).Caption Next i End Sub  Save and run the sample.</li> From the File menu, select Open, and choose any file. Repeat this step several times and you can see the Most Recently Used (MRU) File List in the File menu. Each file you select appears, in order of most recently selected, as a menu item under the File menu. If you select the same file twice, it only appears once in the list. If you select it the second time, it should move to the top of the list. Picking one of these items from the File menu also moves it to the top of the MRU list.

Note that there is a constant named MaxMRU. This constant defines the maximum number of items that appear as recent files on the File menu. In the sample code above, this value is set to 4.</li></ol>

Keywords: kbhowto kbmenu kbcmndlgfileo KB253171

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