PRB: "Argument Not Optional" Error Using DAO 3.5 (168206)

The information in this article applies to:

Microsoft Visual Basic Professional Edition for Windows 4.0
Microsoft Visual Basic Professional Edition for Windows 5.0
Microsoft Visual Basic Enterprise Edition for Windows 4.0
Microsoft Visual Basic Enterprise Edition for Windows 5.0

This article was previously published under Q168206

SYMPTOMS

After porting a Visual Basic 4.0 program that is written using DAO 3.0 (Data Access Objects) to DAO 3.5, the error message:

"Argument Not Optional"

will occur on the Update, Movelast, and CommitTrans methods. This does not happen in Visual Basic 5.0.

CAUSE

In DAO 3.0, the methods listed above do not use optional arguments. They do use optional arguments in DAO 3.5. This is a problem caused by adding the Typed Optional Parameter feature to OLE Automation. Only newer Automation controllers such as Visual Basic 5.0 are going to understand this. Visual Basic 4.0 can accept optional parameters only if they are of the Variant data type. The optional arguments for the methods listed above are not Variant so it doesn't recognize them as optional.

RESOLUTION

There are three options for this problem:

Do not use DAO 3.5 with Visual Basic 4.0. Use DAO 3.0 or lower.
Use the optional arguments listed in the DAO 3.5 Help file.

NOTE: The Help file states that the optional argument constant for Movelast is dbRunAsync. This is not true and it will not work. The actual argument is rdAsyncEnable.
Do not use early binding on the recordset object. For example, the following code will cause the error:
```
      Dim myrecordset as recordset

      Set myrecordset = mydatabase("Table1",dbOpenDynaset)
      myrecordset.Edit
      myrecordset.Update
						
```
Removing the Dim statement will cause it to work as expected.

STATUS

This behavior is by design. Microsoft does not support the use of DAO 3.5 in Visual Basic 4.0. It is recommended that DAO 3.0 or lower be used.

MORE INFORMATION

For information on how to use the methods mentioned above, refer to the Visual Basic online help.

Modification Type:	Major	Last Reviewed:	6/24/2004
Keywords:	kberrmsg kbprb KB168206