Until recently we were using Inno Setup for our installations, something I would like to continue doing, unless we can get an uninstall option in the start menu (thanks Giovanni Galbo), however we now need to GAC some external libraries, something I suspect is only doable (or at least only supported) though the .NET Setup Project.
Is it possible to call a GAC'ing library from another setup application?
According to http://jrsoftware.org/files/is5-whatsnew.htm you should be able to do it with v5.3 and above
Added .NET support (these cause an internal error if used on a system with no .NET Framework present):
* Added new [Files] section flag: gacinstall. * Added new [Files] section parameter: StrongAssemblyName. * Added new constants: {regasmexe}, {regasmexe32}, {regasmexe64}.
Not sure about library, but you can call gacutil.exe to install/uninstall assemblies.
来源：https://stackoverflow.com/questions/61699/adding-assemblies-to-the-gac-from-inno-setup