Compatibility Issues

As DAO has evolved, new objects, methods, and properties have been introduced that render their prior equivalents obsolete. To enhance performance and decrease memory usage, future versions of Microsoft Jet may eliminate support for these obsolete language elements. In order to ease the conversion of applications that use the older objects, methods, and properties, the DAO350.dll file contains two type libraries: the DAO 2.5 type library and the DAO 3.5 type library. These type libraries define the properties and methods that DAO can use.

The DAO 2.5 type library is backward compatible with previous versions of Microsoft Jet and supports all previous objects, methods, and properties. Use this type library if you want existing DAO code to work with Microsoft Jet 3.0 or 3.5 without conversion.

The DAO 3.5 type library removes support for obsolete objects, methods, and properties. Because they are not supported, use of these constructs while the DAO 3.5 type library is in use causes compile errors in your code. The benefit of this behavior is that it allows you to verify that your programs use the latest DAO features by quickly identifying code that uses outdated methods and properties.

In Microsoft Access 97, Visual Basic 5.0, Microsoft Excel 97, and Microsoft Project 97, the Tools menu contains a References command when you are in a code module. Clicking this command gives you a list of object libraries and databases that are available. Two versions of DAO are now available: the DAO 2.5/3.5 compatibility library and DAO 3.5 object library.

By clicking DAO 3.5 Object Library and then recompiling, you can identify any obsolete DAO code with compile errors that place the cursor at the line of code that caused the error.

When you create a new database, the DAO 3.5 Object Library is automatically selected. This ensures that all new DAO code you create uses the new objects. Note that you can’t use both libraries at once.

See Also For a list of obsolete DAO features and their replacement features, search the DAO Help index for “DAO, obsolete features in.”