A Microsoft Access list box is very similar to a combo box, it contains multiple values and allows the user to choose from the list of items. There are obvious differences however, the list box is open at all times and does not allow the user a space to type in values.
There are many other properties available when using the List Box; the user can select multiple items, unlike a combo box, but what can you, as the developer, do with these values? The obvious benefit of a List Box is that it can be configured so that the user can select more than one item at once. The properties of the list box allow the user to pick One choice at a time (if this is the case, it may be as easy to just use a combo box), the user can select multiple items by clicking each one separately (to de-select click the same item twice) or you can allow the user to adjacent or non-adjacent quite easily.
With the help of some VBA programming code, you can add this powerful tool to your Access forms
The following example details using a list box within a form to provide the user with multiple choices of criteria for running a query.
The form contains a list box with suitable criteria values. The user can make their choice from the list and click the Run Query button which will pass their choice to a query, and then opens the query. The form below shows the list box in place:
Microsoft Access List Box visible on the form to allow the user to specify multiple criteria for a query
The list box data is created by using Row Source Type of Table/Query and uses the SQL Row source of:
SELECT DISTINCT tblCompanies.strCompanyCounty FROM tblCompanies UNION SELECT "All" FROM tblCompanies;
This returns the Company Counties based upon tblCompanies and will also return ALL to allow the user to choose to return all of the records if no value is picked.
Now the code behind the command button, cmdOpenQuery, which is required to generate the query results needs to do a couple of things:
The query is created by the code behind the command button within the procedure and the criteria is passed at the creation stage. The associated code is shown below, this is attached to the On Click event of the command button - cmdOpenQuery:
'------------------ Code Start ------------------ Private Sub cmdOpenQuery_Click() On Error GoTo Err_cmdOpenQuery_Click Dim MyDB As DAO.Database Dim qdef As DAO.QueryDef Dim i As Integer Dim strSQL As String Dim strWhere As String Dim strIN As String Dim flgSelectAll As Boolean Dim varItem As Variant Set MyDB = CurrentDb() strSQL = "SELECT * FROM tblCompanies" 'Build the IN string by looping through the listbox For i = 0 To lstCounties.ListCount - 1 If lstCounties.Selected(i) Then If lstCounties.Column(0, i) = "All" Then flgSelectAll = True End If strIN = strIN & "'" & lstCounties.Column(0, i) & "'," End If Next i 'Create the WHERE string, and strip off the last comma of the IN string strWhere = " WHERE [strCompanyCounty] in " & _ "(" & Left(strIN, Len(strIN) - 1) & ")" 'If "All" was selected in the listbox, don't add the WHERE condition If Not flgSelectAll Then strSQL = strSQL & strWhere End If MyDB.QueryDefs.Delete "qryCompanyCounties" Set qdef = MyDB.CreateQueryDef("qryCompanyCounties", strSQL) 'Open the query, built using the IN clause to set the criteria DoCmd.OpenQuery "qryCompanyCounties", acViewNormal 'Clear listbox selection after running query For Each varItem In Me.lstCounties.ItemsSelected Me.lstCounties.Selected(varItem) = False Next varItem Exit_cmdOpenQuery_Click: Exit Sub Err_cmdOpenQuery_Click: If Err.Number = 5 Then MsgBox "You must make a selection(s) from the list" _ , , "Selection Required !" Resume Exit_cmdOpenQuery_Click Else 'Write out the error and exit the sub MsgBox Err.Description Resume Exit_cmdOpenQuery_Click End If End Sub '------------------ Code End -------------------
The code begins by building the IN expression needed to create the criteria for the query, by looping through the list box. The code adds the (') single quote marks around the values and also the (,) comma separator to separate the values in the criteria.
If the user selects the ALL option then the criteria is not required and builds the statement using UNION ALL.
If no selection is made a message box is invoked advising the user that they must make a selection:
Message Box returned when no item(s) are selected from the list box.
Once the item(s) are selected from the list box, and the query has ran the list is cleared using:
'Clear listbox selection after running query For Each varItem In Me.lstCounties.ItemsSelected Me.lstCounties.Selected(varItem) = False Next varItem