Understanding IDO Methods

Standard Methods

All IDOs implement the methods LoadCollection, UpdateCollection, GetPropertyInfo, and Invoke.

• LoadCollection retrieves a collection of rows from the database.
• UpdateCollection takes a set of rows marked for insert, update, or delete, and executes the appropriate SQL code against the database.
• GetPropertyInfo returns detailed information about the properties supported by the IDO.
• Invoke allows you to execute a custom method.

Custom Methods

Custom methods are defined by the developer. You can define custom methods that are implemented in Transact-SQL. Transact-SQL is the preferred programming language because it is easier to use for most of these tasks and because the IDO forms provide useful facilities for defining methods based on these procedures.

There are two kinds of methods based on Transact-SQL stored procedures: methods based on stored procedures without a result set and methods based on stored procedures with a result set.

A stored procedure that does not return a result set may have input and output parameters, but it does not select data to be returned to the caller.

A method that returns a result set (a list of values) to the caller may be used to populate collections. A typical use is to populate drop-down list boxes in forms. You can also bind forms to these returned sets.