Chapter 2. A Tour of the CLR Hosting API

The common language runtime (CLR) hosting API is a set of unmanaged functions and interfaces that a host uses to customize the CLR for its particular application model. Because the CLR has been designed to adapt to a variety of application scenarios, the amount of customization available through the hosting APIs is quite extensive. In most cases, you'll find that your scenario requires only a subset of the total functionality provided by the API. The overview of the hosting API provided in this chapter is intended to give you an idea of the possible customization options so that you can decide which ones apply most to your application's requirements.

Most of the individual features introduced here have entire chapters dedicated to them later in the book. This chapter merely provides the big picture. In addition to explaining the features, I'll describe the design pattern used in the interfaces and provide enough background and samples to get you started using them.

The hosting API is defined in the file mscoree.idl, which can be found in the Include directory in the Microsoft .NET Framework software development kit (SDK). These programming interfaces consist of both unmanaged functions and a set of COM interfaces. The unmanaged functions are public exports from mscoree.dll. Most of these functions are used primarily for CLR initialization, but some are used to discover basic information about the CLR after it is running, such as which version was loaded and where the CLR installation resides on disk.