.NET CLR Interop Overview
Classes in assemblies that are managed by the common language runtime (CLR) can be accessed in X++ code. This feature of Microsoft Dynamics AX is called common language runtime interoperability, or CLR interop.
The CLR interop feature works only in the direction from X++ calling into CLR managed assemblies. It does not support calling X++ classes from a CLR managed assembly.
For information about calling X++ classes from a CLR managed assembly, see .NET Business Connector Overview.
CLR interop is useful when you want your X++ code to access the functionalities in a CLR managed assembly. This includes assemblies that are installed with the .NET Framework, and any assemblies that you create with a language such as C# or Visual Basic.NET.