ACC2: How to Create a Multiple-Selection List Box
ID: Q121356
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The information in this article applies to:
SUMMARY
Advanced: Requires expert coding, interoperability, and multiuser skills.
In a typical list box, you can select only one item at a time. This article
describes how to create a multiple-selection list box in which you can
select more than one item at a time.
NOTE: Microsoft Access version 7.0 has incorporated the MultiSelect
property for list box controls. The MultiSelect property of a list box
specifies whether a user can make multiple selections in a list box and
how the multiple selections can be made.
The following example demonstrates how to create a two-column list box in
Microsoft Access version 2.0. The first column displays an "X" if the row
is selected, or is blank if the row is not selected. The second column
will contain the values that you can select. This article also
demonstrates how to create a semicolon-delimited list of the items
selected in the list box.
This article assumes that you are familiar with Access Basic and with
creating Microsoft Access applications using the programming tools provided
with Microsoft Access. For more information on Access Basic, please refer
to the "Introduction to Programming" manual in Microsoft Access version
1.x, or the "Building Applications" manual in version 2.0.
MORE INFORMATION
The following example demonstrates how to create and use a multiple-
selection list box. This example uses user-defined Access Basic functions
to fill the list box.
- Start Microsoft Access and open the sample database NWIND.MDB.
- Create a new module and type the following lines in the Declarations
section.
NOTE: In the following sample code, an underscore (_) at the end of a
line is used as a line-continuation character. Remove the underscore
from the end of the line when re-creating this code in Access Basic.
Option Explicit
Type MultiSelectArray_TYPE
Selected As String ' Holds "X" or "" indicating selection
Display As Variant ' The value to display in the list box
' row. Example: John Smith
Value As Variant ' The value to store for the row
' selection. Example: 535-86-9328 (John's
' SSN)
End Type
Dim MultiSelectArray() As MultiSelectArray_TYPE
Dim MultiSelectRows
' Flag indicating if the list is being updated (new selection)
' or being filled.
Global UpdateMultiSelect
- Add the following two functions to the module:
Function MultiSelect (fld As Control, id As Long, Row As _
Long, Col As Long, Code As Integer)
'*******************************************************
' CALLED FROM: The RowSourceType property of a list box.
' EXAMPLE:
' RowSourceType: MultiSelect
'*******************************************************
Dim RetVal: RetVal = Null
Select Case Code
Case LB_INITIALIZE
' Is the list being updated by a new selection?
If UpdateMultiSelect Then
' If so, ignore refilling the list.
UpdateMultiSelect = False
Else
' Otherwise, fill the MultiSelect array.
MultiSelectRows = MultiSelectFillArray()
End If
RetVal = MultiSelectRows
Case LB_OPEN
RetVal = Timer ' Unique ID number for control.
Case LB_GETROWCOUNT
' Return the number of rows in the MultiSelect array.
RetVal = UBound(MultiSelectArray) + 1
Case LB_GETCOLUMNCOUNT
' Return the number of columns to display.
RetVal = 2
Case LB_GETCOLUMNWIDTH
RetVal = -1 ' Use the default width.
Case LB_GETVALUE
Select Case Col
Case 0 ' Selected
RetVal = MultiSelectArray(Row).Selected
Case 1 ' Display
RetVal = MultiSelectArray(Row).Display
End Select
Case LB_END ' End
End Select
MultiSelect = RetVal
End Function
Function MultiSelectUpdate (C As Control)
'********************************************************
' CALLED FROM: The AfterUpdate property of the list box.
' EXAMPLE:
' AfterUpdate: =MultiSelectUpdate([<YourListBoxName>])
'********************************************************
' Update the MultiSelect array selection by toggling
' the "X" in the selected row.
Select Case MultiSelectArray(C).Selected
Case ""
MultiSelectArray(C).Selected = "X"
Case "X"
MultiSelectArray(C).Selected = ""
End Select
' Set the flag indicating an update.
UpdateMultiSelect = True
' Requery the list.
C.Requery
End Function
- Create a user-defined function called MultiSelectFillArray() that will
fill the MultiSelect array with the values to be displayed in the list
box. Following are two examples of the MultiSelectFillArray() function.
The first example demonstrates how to fill the array with a list of
names from the Employees table. The second example demonstrates how
to fill the array with a list of field names from the Employees table.
Enter only one of these functions in the module:
Function MultiSelectFillArray ()
'**********************************************************
' PURPOSE: Fills the MultiSelect array with a list of
' names from the Employees table.
' CALLED FROM: The MultiSelect() function's initialization
' code to fill the list box array with values.
'**********************************************************
Dim DB As Database
Dim RS As Recordset
Dim i As Integer
Dim RecordCount As Integer
Set DB = DBEngine.Workspaces(0).Databases(0)
Set RS = DB.OpenRecordset("Employees", DB_OPEN_SNAPSHOT)
' Get record count.
RS.MoveLast
RecordCount = RS.RecordCount
RS.MoveFirst
' Resize the MultiSelect array to the number of Employee
' records.
ReDim MultiSelectArray(0 To RecordCount - 1)
' Fill the MultiSelect array by setting:
' Selected to "" (clearing "X").
' Display to [First Name] space [Last Name].
' Value to [Employee ID].
For i = 0 To RecordCount - 1
MultiSelectArray(i).Selected = ""
MultiSelectArray(i).Display = RS![First Name] & " " _
& RS![Last Name]
MultiSelectArray(i).Value = RS![Employee ID]
RS.MoveNext
Next i
' Return the number of rows in the array (RecordCount).
MultiSelectFillArray = RecordCount
End Function
Function MultiSelectFillArray ()
'**********************************************************
' PURPOSE: Fills the MultiSelect array with a list of
' field names from the Employees table.
' CALLED FROM: The MultiSelect() function's initialization
' code to fill the list box array with values.
'**********************************************************
Dim DB As Database
Dim RS As Recordset
Dim i As Integer
Set DB = DBEngine.Workspaces(0).Databases(0)
Set RS = DB.OpenRecordset("Employees", DB_OPEN_SNAPSHOT)
' Resize the MultiSelect array to the number of Employee
' fields.
ReDim MultiSelectArray(0 To RS.Fields.Count - 1)
' Fill the MultiSelect array by setting:
' Selected to "" (clearing "X").
' Display to the name of the field.
' Value to the name of the field.
For i = 0 To RS.Fields.Count - 1
MultiSelectArray(i).Selected = ""
MultiSelectArray(i).Display = RS(i).Name
MultiSelectArray(i).Value = RS(i).Name
Next i
' Return the number of rows in the array (the number of
' fields).
MultiSelectFillArray = RS.Fields.Count
End Function
- Create a form not based on any table or query.
- Add a list box with the following properties to the form:
Name: EmployeeFields
ControlSource: <blank>
RowSourceType: MultiSelect
RowSource: <blank>
ColumnCount: 2
ColumnWidths: 0.15 in.
BoundColumn: 0
Width: 1.6 in
Height: 1.5 in
AfterUpdate: =MultiSelectUpdate([EmployeeFields])
- View the form in Form view. Depending on which example you chose in
step 4, you will see a list box containing either a list of names
from the Employees table or a list of field names from the Employees
table. You can select or unselect an item in the list box by clicking
the item. An item is selected if an "X" appears in the column to the
left of the item. Note that if you press the UP ARROW and DOWN ARROW
keys to move the pointer up or down in the list box, each item that you
move past is toggled.
NOTE: If you manually requery the list box by using the Requery macro
action or the Requery method, or by pressing the F9 key in the list box,
all the selections in the list box will be cleared.
How to Create a Semicolon-Delimited List of Items Selected in List Box
The following example demonstrates how to use the MultiSelect array to
create a semicolon-delimited list of the items selected in the list box:
- Add the following function to the module that you created in step 2
above:
Function MultiSelectSemicolonList ()
Dim i
Dim Result
Result = ""
For i = 0 To UBound(MultiSelectArray)
If MultiSelectArray(i).Selected = "X" Then
Result = Result & MultiSelectArray(i).Display & "; "
End If
Next i
' Remove the last semicolon.
If Result <> "" Then Result = Left(Result, Len(Result) - 1)
MultiSelectSemicolonList = Result
End Function
- Add a text box with the following property to the form that you
created in step 5 above:
ControlSource: =MultiSelectSemicolonList()
- View the form in Form view. Note that when you make selections in the
list box, the text box is updated to display a list of the items
selected.
REFERENCES
For more information about using an Access Basic function to fill a list
box, search for "filling list boxes/combo boxes," and then "Filling a List
Box or Combo Box Using an Access Basic Function" using the Microsoft Access
version 2.0 Help menu.
For more information about MultiSelect list boxes in Microsoft Access
version 7.0, search for "MultiSelect Property" using the Microsoft Access
for Windows 95 Help Index.
Additional query words:
multiselection
Keywords : kbusage FmrCodeb
Version : 2.0
Platform : WINDOWS
Issue type : kbhowto
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