You decide which custom methods (described in "ActiveX Custom Methods") to make available to your client application developer by designing the opaque types and associated support routines of the server project. The server project design process is the same as designing a limited-feature DataBlade module. For a review of that process, see Chapter 2, "Designing DataBlade Modules." In addition, keep the following ActiveX-specific considerations in mind:

• You must implement the client project of an ActiveX value object in C++.
• You can implement the server project in C++ or C. For information on the advantages and disadvantages of choosing one language over the other, see "Client and Server Projects".

• When you define the opaque type that you intend to encapsulate as an ActiveX value object, BladeSmith enforces these rules:
  • You must define the internal structure of the opaque type.
  • The opaque type must be of a fixed size.
  • The opaque type cannot contain members that are large objects or variable in size.
  • The opaque type can contain members that are opaque types only if they are implemented in C++.
• You cannot import interfaces or opaque types from other DataBlade modules.
• The following opaque type routine categories are not supported for either the client or server projects of an ActiveX value object:
  • Contains large objects
  • Type insert/delete notification
• The following opaque type routine categories have no meaning for database clients. Thus, although you can implement these routines for the server project, they are not made available to the client application developer as ActiveX custom methods:
  • Binary send/receive with client
  • Text file import/export
  • Binary file import/export
  • Hash
• The following ActiveX custom methods do not have equivalents in the server project:
  • IsNull
  • SetNullFlag