这是什么? Reference assemblies DLL?

Reference assemblies are a specific type of DLL (Dynamic Link Library) file used primarily by developers to reference .NET Framework types and interfaces without actually linking against the runtime components. These assemblies provide a way for the compiler and development tools to understand the structure, methods, properties, and events available in the .NET Framework libraries. They serve as a specification layer that helps maintain compatibility and consistency across different versions of the .NET Framework, ensuring that developers can write code against a standardized set of APIs without having the actual runtime dependencies.