Adding a blank (null) to a combobox selection list.

I have several combo boxes that act as filters for a listbox on the same form.
When the form opens, the combo boxes are blank and all records are shown in the listbox.

When a selection is made in one or more of the combo boxes, the list is filtered.  That all works fine.

However, I would like an easy way to set a combobox back to null, thus removing it's value as a filter.  I think the easiest way for a user to understand/accomplish would be if there was a "blank" selection in the combo box selections.  How can I add one?

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Create a command button and reference your combos and set the value = ""

i.e. cboName1="" ' place this or something similiar in the code for the command button.
To a blank to combo box:

SELECT tblName.FieldName, tblName.FieldName2
FROM tblName
GROUP BY tblName.FieldName, tblName.FieldName2
ORDER BY tblName.FieldName
UNION select '', -1 from tblName.FieldName;

SELECT tblName.FieldName, tblName.FieldName2
FROM tblName
GROUP BY tblName.FieldName, tblName.FieldName2
ORDER BY tblName.FieldName
UNION select '', -1 from tblName; ' if you add more columns (fields) to your combo then add same number of -1
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this is the same as adding <All> to the top of your combobox and users will likely understand that better. You do that by making the queries your comboboxes are using as rowsources be UNION queries. Can you give us an example of the SQL for one of the comboboxes?

You will likely also need to change you filtering code to ignore the <All>. Can you give us the filtering code for one of the combobs also?

DatabaseMX (Joe Anderson - Microsoft Access MVP)Database Architect / Systems AnalystCommented:
Here is a general purpose function you can use in many different ways, not just for this:

1) Create a new VBA module
2) Paste in all the code below
3) Add the function call below to the On Dbl Click event - **on the property sheet* - of any control (text or combo box) you want the user to be able to clear. To clear the control, the user holds down the Control Key and double clicks!  Note that you can use a different vb key if you don't like 'Control'. However, 'Control / Clear' ... get the drift?


Note that you can select several controls (that you want to be able to clear) at one time, then paste in the line of code on the On Dbl Click event.  

Option Compare Database
Option Explicit

   'Return the state of keyboard key requested....
    Declare Function adiSWA_GetKeyState Lib "user32.dll" Alias "GetKeyState" (ByVal nKey%) As Integer

Function SSF_SetToNull() As Boolean

    SSF_SetToNull = False                                    'Initialize
    If SWA_GetKeyState(vbKeyControl) Then     'Check for Control+double click
        Screen.ActiveControl = Null                         'Null out active control
        SSF_SetToNull = True                                  'Successful
    End If

End Function

Function SWA_GetKeyState(vbKeyName)

    If adiSWA_GetKeyState(vbKeyName) < 0 Then
        SWA_GetKeyState = True
        SWA_GetKeyState = False
    End If

End Function
What type of combo box is this?  If it's just a value list, you might get away with just putting two semi-colons.  ex.  apples:oranges;;squash    would display as



Not exactly null, but... If the list looks to a query or table, can you add a null entry there?
Otherwise, I'd go with the old standby "ALL" selection as others have suggested.
how about

Private Sub Combo6_DblClick(Cancel As Integer)
Me.Combo6.Value = ""
End Sub

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snyperjAuthor Commented:
Thanks to all who suggested.  I found jefftwilleys the quickest and easiest to implement but I appreciate all who gave suggestions.
DatabaseMX (Joe Anderson - Microsoft Access MVP)Database Architect / Systems AnalystCommented:

Not to take anything away from Jeff, but just note however, that does not set the combo box to Null.  It sets it to an Empty String ... and there is a big difference  ...  which may or may not make a difference in some cases.  
Your question asked "Easy way to set a combobox back to null" ...

snyperjAuthor Commented:
understood. Thanks.
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