Below you will find a sample project (received from one of our clients) that contains a custom action which helps you test an Oracle database connection. The custom action was implemented based on the example from the "Connecting to Oracle Database" article.
During the installation, the server, the username and the password related to the database can be introduced on a dialog while a search is performed (defined in the "Search" page) to see if Oracle is installed on the machine. If not, an error message is displayed and the installation is blocked.
If Oracle is found on the machine the connection is tested and if it returns a value equal to 0, the connection succeeded and the installation continues. In case the Oracle throws an error, that error will be displayed in a message box.