Metadata (CLI)

Metadata (CLI)

Metadata, in the Common Language Infrastructure (CLI), refers to certain data structures embedded within the Common Intermediate Language code that describes the high-level structure of the code. Metadata describes all classes and class members that are defined in the assembly, and the classes and class members that the current assembly will call from another assembly. The metadata for a method contains the complete description of the method, including the class (and the assembly that contains the class), the return type and all of the method parameters.

A CLI language compiler will generate the metadata and store this in the assembly containing the CIL. When the run-time executes CIL it will check to make sure that the metadata of the called method is the same as the metadata that is stored in the calling method. This ensures that a method can only be called with exactly the right number of parameters and exactly the right parameter types.

The Windows Runtime application platform, present in Windows 8 and Windows Phone 8, makes use of the CLI metadata format to describe component interfaces for code written in any of the supported programming languages. A difference in use within within the Common Language Runtime is that an assembly typically do not contain any CIL instructions.