Microsoft KB Archive/168206

= PRB: "Argument Not Optional" Error Using DAO 3.5 =

Article ID: 168206

Article Last Modified on 6/24/2004

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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 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.

Keywords: kberrmsg kbprb KB168206

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