Metadata

Every component in .NET contains metadata. Metadata describes the runtime types, classes, interfaces, structs, and all entities within a .NET component. Metadata also provides implementation and layout information that the .NET runtime makes use of to JIT compile IL code.

Metadata is available to all tools through two different sets of APIs. There exists a set of low-level, unmanaged APIs and a set of managed APIs that can be used to gather information about a .NET component. There also exists a set of APIs for emitting Metadata. This emit API is used by compilers during compilation of a given source language into IL for the .NET runtime. A full description of the Metadata APIs and infrastructure would require another book in itself, but this text will present a small sample of how to use the Reflection API to inspect a .NET component.