SUMMARYOut-of-the-box, the only way of coding RS232 serial communications applications in the .NET environment is to import the outdated and somewhat limited MSComm ActiveX control. This article describes the development of a lean, multithreaded, and modern RS232 base class library in C# managed code. The library uses Platform Invocation Services to interact with the Win32 API directly. Application programmers can use the library from any .NET language through inheritance; the article explores examples written in C# and Visual Basic .NET.