The information in this article applies to:
- Professional and Enterprise Editions of Microsoft Visual Basic,
16-bit and 32-bit, for Windows, version 4.0
- Standard and Professional Editions of Microsoft Visual Basic for
Windows, version 3.0
SYMPTOMS
Code that doesn't refer explicitly to the Name property of the dynaset
object, but instead uses the dynaset's old default property, Name, compiles
and runs correctly when using Visual Basic 3.0. However, the compilation
fails under Visual Basic 4.0, stopping and giving a "Type mismatch" error
on lines where the default property is used.
CAUSE
With Visual Basic 4.0, the default value of the dynaset object is no longer
the Name property. When you refer to a dynaset object without referring to
any properties, Visual Basic 4.0 interprets this to be a reference to the
dynaset object itself.
RESOLUTION
Change the code to refer explicitly to all properties. When assigning a
string to the RecordSource property of a data control, instead of using
Dim ds as Dynaset
Data1.RecordSource = ds
use the following:
Dim ds as Dynaset
Data1.RecordSource = ds.Name
NOTE: The Dynaset object is provided for backwards compatibility. Use of
the new enhanced RecordSet object is recommended.
STATUS
This behavior is by design.
MORE INFORMATION
Steps to Reproduce
- Start Visual Basic.
- On the File menu, click New Project.
- Double-click the data control button in the Toolbox to add a new data
control, named Data1, to the form.
- Add a command button to the form by clicking the command button icon in
the Toolbox.
- Insert the following code in the Command1_Click procedure, changing the
path with the OpenDatabase statement to refer to where your copy of
BIBLIO.MDB is located. In addition, because the code below uses old
style syntax, when running under Visual Basic 4.0 you must have
"Microsoft DAO 2.5/3.0 Compatibility Layer" checked in the References
dialog box.
Sub Command1_Click ()
Dim db As Database
Dim ds As Dynaset
Set db = OpenDatabase("c:\vb\biblio.mdb")
Set ds = db.CreateDynaset("Authors")
'set Data1's RecordSource to the Name of the ds object
'works with Visual Basic 3.0, doesn't work with Visual Basic 4.0
Data1.RecordSource = ds
End Sub
- On the Run menu, click Start (ALT, R, S) or press F5. When compiled
under Visual Basic 3.0, the above code works as expected and
Data1.RecordSource has the value "Authors" when the procedure exits.
With Visual Basic 4.0, the program fails to run and flags the last line
in the procedure with a 'Type mismatch' error. Changing the last line
from
Data1.RecordSource = ds
to the following
Data1.RecordSource = ds.Name
resolves the problem.
The RecordSource property of a data control expects a string value, and
that is what is returned as the default property of a dynaset in Visual
Basic 3.0. In Visual Basic 4.0, referring to a dynaset by its name only is
interpreted to mean that you are referring to the recordset object itself.
Because RecordSource expects a string, Visual Basic raises the "Type
mismatch" error when an attempt is made to assign a recordset object to
RecordSource.
NOTE: The Name property of a dynaset or recordset object refers to the name
of the table, QueryDef, or SQL statement used to create it (see the online
help for Name).
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