See the question. I want to see the methods and classes offered by a DLLs library.
Outside of Visual Studio, you can use a dependency tool which is able to inspect DLL and EXE imports and exports, it integrates with the shell and is very easy to use. It comes with some Microsoft SDKs. If you want to avoid the hassle of downloading and installing SDK just because of this, easy download links for all 32b/64b platforms are available at http://www.dependencywalker.com/
Microsoft documentation (no download) is available at MicroSoft Technet
Similar functionality is also available in SysInternals Process Explorer - best suited when inspecting running processes.