How to Determine If a DAO VB6 Recordset Is Locked: AddNew Method

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How to Determine If a DAO VB6 Recordset Is Locked: AddNew Method

If you are working with DAO (Data Access Objects) in VB6, you may encounter situations where you need to add new records to a database table using a recordset, but you also need to check if the recordset is locked by another process or user. In this blog post, we will explore one way to do that using the AddNew method, which can return an error code indicating if the recordset is locked or not. We will also discuss some related concepts and issues, including transactions, concurrency, and DAO vs. ADO.

1. Understanding DAO and Recordsets

DAO is a Microsoft technology that provides a set of objects and methods for accessing and manipulating data in databases. DAO can work with various database formats, such as Access, Excel, or SQL Server, and supports features like transactions, locking, and indexing. One of the main objects in DAO is the Recordset, which represents a set of records from a table or query. A recordset can be opened in different modes, such as read-only, updatable, or dynamic, and can be navigated using methods like MoveFirst, MoveNext, or Find.

2. Using AddNew Method

To add a new record to a recordset, you can use the AddNew method, which creates a new record and positions the recordset at that record. You can then set the values of the fields in the record using the Fields collection, and then call the Update method to save the changes to the database. However, before calling AddNew, you should check if the recordset is locked by another user or process, to avoid conflicts and errors. One way to do that is to use the error handling mechanism of VB6, which can capture the error code returned by AddNew and interpret it as a locking error.

3. Handling Locking Errors

When AddNew encounters a locking error, it raises an exception that can be caught by a Try...Catch block or an On Error statement. The error code returned by AddNew for a locking error is 3186, which means "Could not update; currently locked by another session on this machine." This error code indicates that the recordset is locked by another process or user, and that you should retry the operation later or inform the user of the conflict. You can also use other error codes to distinguish between different kinds of errors, such as syntax errors, data validation errors, or network errors.

Conclusion

In summary, to determine if a DAO VB6 recordset is locked before adding a new record, you can use the AddNew method and capture the error code returned. You should also be aware of other issues related to transactions, concurrency, and DAO vs. ADO, which may affect the performance and reliability of your code. By following good practices and testing your code thoroughly, you can avoid common pitfalls and improve your productivity as a developer. Finally, if you are interested in investing in cryptocurrencies, you should also pay attention to factors like market trends, risk management, and security, and seek professional advice when necessary.