Microsoft KB Archive/170884

= HOWTO: Sort a ListView Control by Date =

Article ID: 170884

Article Last Modified on 2/24/2005

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APPLIES TO


 * Microsoft Visual Basic 6.0 Learning Edition
 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition
 * Microsoft Visual Basic 5.0 Control Creation Edition

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This article was previously published under Q170884



SUMMARY
When using a Listview control, you can set the Sorted property for the control to sort the list alphabetically. However, the Listview control does not expose a property or method for sorting a list by date. This article presents a method that you can use to sort a Listview control by date.



MORE INFORMATION
WARNING: One or more of the following functions are discussed in this article; VarPtr, VarPtrArray, VarPtrStringArray, StrPtr, ObjPtr. These functions are not supported by Microsoft Technical Support. They are not documented in the Visual Basic documentation and are provided in this Knowledge Base article "as is." Microsoft does not guarantee that they will be available in future releases of Visual Basic.

To sort data in a ListView control by date, it is necessary to provide a comparison function to the control via AddressOf.

NOTE: Using this approach, you will sort the data in the control but not the ListItems collection. Therefore, if you must read the data from the list in sorted order, it is necessary to step through the actual list rather than the ListItems collection.

Step-by-Step Example
 Start a new Visual Basic project. Form1 is created by default. On the Project menu, click Components, select the Microsoft Windows Common Controls 5.0 check box, and then click OK.

NOTE: You can also use Visual Basic 6.0 and select the Microsoft Windows Common Controls 6.0 check box with only one minor change, as noted below. Add a Module to the project. Draw a ListView control on Form1.  Add the following code to Form1: Option Explicit

Private Sub Form_Load

Dim clmAdd As ColumnHeader Dim itmAdd As ListItem

'Add two Column Headers to the ListView control Set clmAdd = ListView1.ColumnHeaders.Add(Text:="Name") Set clmAdd = ListView1.ColumnHeaders.Add(Text:="Date")

'Set the view property of the Listview control to Report view ListView1.View = lvwReport

'Add data to the ListView control Set itmAdd = ListView1.ListItems.Add(Text:="Joe") itmAdd.SubItems(1) = "05/07/97"

Set itmAdd = ListView1.ListItems.Add(Text:="Sally") itmAdd.SubItems(1) = "04/08/97"

Set itmAdd = ListView1.ListItems.Add(Text:="Bill") itmAdd.SubItems(1) = "05/29/97"

Set itmAdd = ListView1.ListItems.Add(Text:="Fred") itmAdd.SubItems(1) = "05/17/97"

Set itmAdd = ListView1.ListItems.Add(Text:="Anne") itmAdd.SubItems(1) = "04/01/97"

End Sub

' Use this line of code for Common Controls 5.0: Private Sub ListView1_ColumnClick(ByVal ColumnHeader As _             ComctlLib.ColumnHeader) ' For Common Controls 6.0, uncomment the line below and comment the line above. 'Private Sub ListView1_ColumnClick(ByVal ColumnHeader As _             MSComctlLib.ColumnHeader)

Dim strName As String Dim dDate As Date Dim lngItem As Long

'Handle User click on column header If ColumnHeader.Text = "Name" Then 'User clicked on Name header ListView1.Sorted = True       'Use default sorting to sort the ListView1.SortKey = 0         'items in the list Else ListView1.Sorted = False      'User clicked on the Date header 'Use our sort routine to sort 'by date SendMessage ListView1.hWnd, _ LVM_SORTITEMS, _ ListView1.hWnd, _ AddressOf CompareDates End If

'Refresh the ListView before writing the data ListView1.Refresh

'Loop through the items in the List to print them out in       'sorted order. 'NOTE: You are looping through the ListView control because when _ 'sorting by date the ListItems collection won't be sorted.

For lngItem = 0 To ListView1.ListItems.Count - 1 ListView_GetListItem lngItem, ListView1.hWnd, strName, dDate Next

End Sub   Add the following code to Module1: Option Explicit

'Structures

Public Type POINT x As Long y As Long End Type

Public Type LV_FINDINFO flags As Long psz As String lParam As Long pt As POINT vkDirection As Long End Type

Public Type LV_ITEM mask As Long iItem As Long iSubItem As Long State As Long stateMask As Long pszText As Long cchTextMax As Long iImage As Long lParam As Long iIndent As Long End Type

'Constants Private Const LVFI_PARAM = 1 Private Const LVIF_TEXT = &H1

Private Const LVM_FIRST = &H1000 Private Const LVM_FINDITEM = LVM_FIRST + 13 Private Const LVM_GETITEMTEXT = LVM_FIRST + 45 Public Const LVM_SORTITEMS = LVM_FIRST + 48

'API declarations

Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _       ByVal hWnd As Long, _        ByVal wMsg As Long, _        ByVal wParam As Long, _        ByVal lParam As Long) As Long

'Module Functions and Procedures

'CompareDates: This is the sorting routine that gets passed to the 'ListView control to provide the comparison test for date values.

Public Function CompareDates(ByVal lngParam1 As Long, _                                  ByVal lngParam2 As Long, _                                   ByVal hWnd As Long) As Long

Dim strName1 As String Dim strName2 As String Dim dDate1 As Date Dim dDate2 As Date

'Obtain the item names and dates corresponding to the 'input parameters

ListView_GetItemData lngParam1, hWnd, strName1, dDate1 ListView_GetItemData lngParam2, hWnd, strName2, dDate2

'Compare the dates 'Return 0 ==> Less Than '      1 ==> Equal '      2 ==> Greater Than

If dDate1 < dDate2 Then CompareDates = 0 ElseIf dDate1 = dDate2 Then CompareDates = 1 Else CompareDates = 2 End If

End Function

'GetItemData - Given Retrieves

Public Sub ListView_GetItemData(lngParam As Long, _                                     hWnd As Long, _                                      strName As String, _                                      dDate As Date) Dim objFind As LV_FINDINFO Dim lngIndex As Long Dim objItem As LV_ITEM Dim baBuffer(32) As Byte Dim lngLength As Long

'       ' Convert the input parameter to an index in the list view '       objFind.flags = LVFI_PARAM objFind.lParam = lngParam lngIndex = SendMessage(hWnd, LVM_FINDITEM, -1, VarPtr(objFind))

'       ' Obtain the name of the specified list view item '       objItem.mask = LVIF_TEXT objItem.iSubItem = 0 objItem.pszText = VarPtr(baBuffer(0)) objItem.cchTextMax = UBound(baBuffer) lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _                               VarPtr(objItem)) strName = Left$(StrConv(baBuffer, vbUnicode), lngLength)

'       ' Obtain the modification date of the specified list view item '       objItem.mask = LVIF_TEXT objItem.iSubItem = 1 objItem.pszText = VarPtr(baBuffer(0)) objItem.cchTextMax = UBound(baBuffer) lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _                               VarPtr(objItem)) If lngLength > 0 Then dDate = CDate(Left$(StrConv(baBuffer, vbUnicode), lngLength)) End If

End Sub

'GetListItem - This is a modified version of ListView_GetItemData ' It takes an index into the list as a parameter and returns ' the appropriate values in the strName and dDate parameters.

Public Sub ListView_GetListItem(lngIndex As Long, _                                     hWnd As Long, _                                      strName As String, _                                      dDate As Date) Dim objItem As LV_ITEM Dim baBuffer(32) As Byte Dim lngLength As Long

'       ' Obtain the name of the specified list view item '       objItem.mask = LVIF_TEXT objItem.iSubItem = 0 objItem.pszText = VarPtr(baBuffer(0)) objItem.cchTextMax = UBound(baBuffer) lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _                               VarPtr(objItem)) strName = Left$(StrConv(baBuffer, vbUnicode), lngLength)

'       ' Obtain the modification date of the specified list view item '       objItem.mask = LVIF_TEXT objItem.iSubItem = 1 objItem.pszText = VarPtr(baBuffer(0)) objItem.cchTextMax = UBound(baBuffer) lngLength = SendMessage(hWnd, LVM_GETITEMTEXT, lngIndex, _                               VarPtr(objItem)) If lngLength > 0 Then dDate = CDate(Left$(StrConv(baBuffer, vbUnicode), lngLength)) End If

End Sub  Save your project.</li> Press the F5 key to run the application. Click the Date column header to sort the items in the list by date.</li></ol>

Keywords: kbhowto kbapi KB170884

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