An Error object contains details about data access errors, each of which pertains to a single operation involving DAO.
Any operation involving DAO can generate one or more errors. For example, a call to an ODBC server might result in an error from the database server, an error from ODBC, and a DAO error. As each such error occurs, an Error object is placed in the Errors collection of the DBEngine object. A single event can therefore result in several Error objects appearing in the Errors collection.
When a subsequent DAO operation generates an error, the Errors collection is cleared, and one or more new Error objects are placed in the Errors collection. DAO operations that don't generate an error have no effect on the Errors collection.
The set of Error objects in the Errors collection describes one error. The first Error object is the lowest level error (the originating error), the second the next higher level error, and so forth. For example, if an ODBC error occurs while trying to open a Recordset object, the first Error object — Errors(0) — contains the lowest level ODBC error; subsequent errors contain the ODBC errors returned by the various layers of ODBC. In this case, the ODBC driver manager, and possibly the driver itself, return separate Error objects. The last Error object — Errors.Count-1 — contains the DAO error indicating that the object couldn't be opened.
Enumerating the specific errors in the Errors collection enables your error-handling routines to more precisely determine the cause and origin of an error, and take appropriate steps to recover. On both Microsoft Jet and ODBCDirect workspaces, you can read the Error object’s properties to obtain specific details about each error, including:
|?||The Description property, which contains the text of the error alert that will be displayed on the screen if the error is not trapped.|
|?||The Source property, which identifies the object that raised the error. This is particularly useful when you have several Error objects in the Errors collection following a request to an ODBC data source.|
|?||The HelpFile and HelpContext properties, which indicate the appropriate Microsoft Windows Help file and Help topic, respectively, (if any exist) for the error.|
Note When programming in Microsoft Visual Basic for Applications (VBA), if you use the New keyword to create an object that subsequently causes an error before that object has been appended to a collection, the DBEngine object's Errors collection won't contain an entry for that object's error, because the new object is not associated with the DBEngine object. However, the error information is available in the VBA Err object.
Your VBA error-handling code should examine the Errors collection whenever you anticipate a data access error. If you are writing a centralized error handler, test the VBA Err object to determine if the error information in the Errors collection is valid. If the Number property of the last element of the Errors collection (DBEngine.Errors.Count - 1) and the value of the Err object match, you can then use a series of Select Case statements to identify the particular DAO error or errors that occurred. If they do not match, use the Refresh method on the Errors collection.