Advance Steel (starting with version 2015) supports loading and executing external code in the form of .NET assemblies. These are commonly referred to as "Plugins" or "Addins".
The Advance Steel API is fully accessible by any language compatible with the Microsoft .NET Framework 8, such as Visual C# or Visual Basic .NET (VB.NET). However, the focus of this documentation is developing applications using Visual C#.
The steps required to create, load and get code inside such an assembly are detailed in a series of walkthroughs.