Microsoft KB Archive/170358

= PRB: Masked Edit May Not Show Empty When Bound Field is Null =

Article ID: 170358

Article Last Modified on 6/29/2004

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APPLIES TO


 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 4.0 Enterprise Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition

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This article was previously published under Q170358



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.



Steps to Reproduce Behavior
 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." Add a Data Control to Form1. Add a Masked Edit Control to Form1. Set the DataSource property to "Data1." Add a Text Box to Form1. Set the DataSource property to "Data1."  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  Press the F5 key to run the application.</li> 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.</li></ol>

Keywords: kbprb KB170358

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