Most Custom Servers are implemented as a .NET DLL. This option is generally preferred because:
Development is supported by all the services of the program development environment, such as syntax checking, debugging, and Microsoft IntelliSense.
If table checkpoint and output value support is needed, this support is available only when implementing the Custom Server as a .NET DLL.
A Custom Server implemented as a .NET DLL can perform part of its Test Record functions in the UFT One context and part in the context of the application being tested. For more information, see Using a .NET DLL to Extend Support for a Custom Control, and the API Reference.
For information on run-time contexts, see Selecting the Custom Server Run-Time Context Depending on the Test Function.