When creating a multi-form application, there some basic rules and concepts you need to know:

• The forms of a multi-form application are always created as separate, independent forms
• The forms are joined together by choosing one of the forms as the main form of the application and then including the other forms in it. At run-time the main form controls the other forms.
• A form cannot see what is inside another form (components or logic). All it knows about the other form are the properties, events and methods of the form itself.
• In most applications you use user-defined events, properties and methods for a form in addition to the standard ones. Typically the information that is custom-defined is application-specific, in other words it deals with the object the form works with, for example employees, invoices, departments.
• You create the user-defined events, methods and properties for the member forms, not the main form.