Concept Distinguish: GAC VS sidebyside

Side-by-side assembly

Side-by-side technology is a standard for executable files in Microsoft Windows XP and later versions that attempts to reduce DLL hell. Side-by-side technology is also known as WinSxS or SxS. Executables that include an SxS manifest are designated SxS assemblies.

DLL hell designates a group of problems that arise from the use of dynamic-link libraries in Microsoft Windows. Problems include version conflicts, missing DLLs, duplicate DLLs, and incorrect or missing registration. In SxS, Windows stores multiple versions of a DLL in the WinSXS subdirectory of the Windows directory, and loads them on demand. This reduces dependency problems for applications that include an SxS manifest.

Microsoft Visual C++ 2005 and 2008 employ SxS with all C runtime libraries. However, runtime libraries in Visual C++ 2010 no longer use this technology.

GAC ( Global Assembly Cache )

The Global Assembly Cache or GAC is a machine-wide .NET assemblies cache for Microsoft's CLR platform. The approach of having a specially controlled central repository addresses the shared library concept and helps to avoid pitfalls of other solutions that lead to drawbacks like DLL hell. CLR will firstly search in GAC for assembly loading and then get into app specific directory / path.