Q170358: PRB: Masked Edit May Not Show Empty When Bound Field is Null
Article: Q170358
Product(s): Microsoft Visual Basic for Windows
Version(s): 4.0 5.0
Operating System(s):
Keyword(s): kbVBp500 kbGrpDSVB
Last Modified: 11-JAN-2001
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Visual Basic Professional Edition for Windows, versions 4.0, 5.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 4.0, 5.0
-------------------------------------------------------------------------------
SYMPTOMS
========
The Masked Edit control may not show an empty value when it is bound to a field
in a Microsoft Access table. If you set the Mask Property of the control and the
bound field is null, the control will not display an empty mask. Instead, it
will show the value from the last non-null field. If the first record displayed
has a null field, the control will show an empty mask. However, as soon as the
control displays a non-null field it will not display an empty mask for any
other empty field. If the Mask Property is not set, null fields will display as
empty in the Masked Edit control.
RESOLUTION
==========
To work around this problem, you can change the text property of the Masked Edit
control to an empty string when the bound field to contains a null value:
Private Sub Data1_Reposition()
'Check to see if the record is empty or contains
'a zero length string.
'Note: The AllowZeroLength property of the field must be True.
If IsNull(Data1.Recordset("Phone")) Or _
Data1.Recordset("Phone") = "" Then
'Set the Masked Edit Box to an empty string
'Note: This sets the DataChanged for MaskEdBox1 to True
MaskEdBox1.Text = "(___) ___-____"
bFieldNull = True 'The field has no value
Else
bFieldNull = False 'The field has a value
End If
'Set the mask for the control
MaskEdBox1.Mask = "(###) ###-####"
End Sub
Private Sub Data1_Validate(Action As Integer, Save As Integer)
If MaskEdBox1.DataChanged Then
'Check to see if the Masked Edit Box has an empty string
'and that the field was empty when you moved to this record
If MaskEdBox1.Text = "(___) ___-____" And bFieldNull Then
'If the control has an empty string and the field is null
'set the DataChanged to False so that you don't
'update the field
MaskEdBox1.DataChanged = False
'If the control now has an empty string but the field
'had a value when moved to this record you want to remove
'the value from the field
ElseIf MaskEdBox1.Text = "(___) ___-____" _
And Not bFieldNull Then
'Turn the mask off so you can save an empty record
MaskEdBox1.Mask = ""
MaskEdBox1.Text = ""
Data1.UpdateRecord 'update the bound controls
End If
End If
End Sub
STATUS
======
This behavior is by design.
MORE INFORMATION
================
Steps to Reproduce Behavior
---------------------------
1. Create a new project. Add the Masked Edit Control to the project.
NOTE: In Visual Basic 4.0, click Custom Controls on the Tools menu and check
"Microsoft Masked Edit Control." In Visual Basic 5.0, click Components on the
Project menu and check "Microsoft Masked Edit Control 5.0."
2. Add a Data Control to Form1.
3. Add a Masked Edit Control to Form1. Set the DataSource property to "Data1."
4. Add a Text Box to Form1. Set the DataSource property to "Data1."
5. Add the following code to Form1:
Dim bFieldNull As Boolean
Dim db As Database
Dim rs As Recordset
Private Sub Form_Load()
'Create a table with a phone field. Put some records into it.
'Some records will have a phone value, some will be empty
Dim fd As Field
Dim td As TableDef
Dim i As Integer
On Error GoTo myerr ' The next line will cause an error if the
'database already exists
'Create a database containing a table, "Table1", which contains
'one field, "Phone".
Set db = Workspaces(0).CreateDatabase("MaskTest", _
dbLangGeneral)
Set td = db.CreateTableDef("Table1")
Set fd = td.CreateField("Phone", dbText, 14)
fd.AllowZeroLength = True
td.Fields.Append fd
db.TableDefs.Append td
'Add data to the Phone Field for even number records. The Phone
'Field for odd number records will remain null.
Set rs = db.OpenRecordset("table1")
For i = 1 To 6
rs.AddNew
If i Mod 2 = 0 Then
rs("phone") = "(234) 654-9876"
End If
rs.Update
Next
db.Close
LoadTable 'Call the LoadTable sub
Exit Sub
myerr:
LoadTable 'Call the LoadTable sub
End Sub
Private Sub LoadTable()
'Set the Recordset for the Data Control to all the records
'in Table1 and bind the Phone field to the Masked Edit control.
Set db = DBEngine(0).OpenDatabase("MaskTest")
Set rs = db.OpenRecordset("Table1")
rs.MoveFirst
Set Data1.Recordset = rs
MaskEdBox1.Mask = "(###) ###-####"
text1.DataField = "Phone"
MaskEdBox1.DataField = "Phone"
End Sub
6. Press the F5 key to run the application.
7. Move through the records using the Data Control. Note that the Masked Edit
Control does not update properly when the bound field is null. To work around
this problem so that the Masked Edit control shows empty records when the
bound field's value is null, add the code from the RESOLUTION section in this
article to the Form1. Press the F5 key to run the application.
(c) Microsoft Corporation 1997, All Rights Reserved.
Contributions by Brian Combs, Microsoft Corporation
Additional query words:
======================================================================
Keywords : kbVBp500 kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVBA500 kbVB500 kbVB400Search kbVB400
Version : 4.0 5.0
Issue type : kbprb
=============================================================================
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
Copyright Microsoft Corporation 1986-2002.