How to make Internet Explorer add-on for IE7,
IE8, IE9 and IE11 in VB.NET, C#, C++
Version-neutrality - your IE add-ons work for IE6 - IE11
Add-in Express delivers version-neutral interop assemblies based on the Internet Explorer 6.0 type library. Using these assemblies you can program version-neutral add-ons compatible with all Internet Explorer versions, i.e. from IE 6 through IE 11.
You can develop add-ons for a specific IE version, too. For example, if you want your plug-in to work with IE8, IE9, IE10 and IE11 - simply use the interop assembly for the IE 8 type library, and your add-in will load into that version and all subsequent IE versions. You can choose any interop assembly regardless of the actual IE version installed on your development PC.
Stop counting bits - your IE plug-ins are bit-insensitive
By default, all your solutions based on Add-in Express are compiled for the Any CPU platform. So all your IE plug-ins are bit-insensitive (or bit-neutral). However, to make your IE add-ons more secure and stable, Add-in Express isolates each of them in a separate application domain by using a special Win32 "shim", the Add-in Express Loader. There are two versions of the loader, one for the 32-bit and the other for 64-bit CPU. Both versions are included in IE add-on setup projects and are separately registered for 32- and 64-bit versions of Internet Explorer. A setup project created by Add-in Express will require only minor modifications: you can adjust simple properties such as SupportUrl, add required files, etc. All custom actions needed for add-on registration are generated automatically.