There are different office version, different com type libraries for managing them.
Could anyone tell me how should i write the code to operate on different Excel version? What about PIA for office, should I include them all with the project?
How to solve the problem of office multiversioning?
This is not fundamentally different from writing a .NET program and expecting it to run on windows 98 as well as Windows 7. The first choice is obvious, you'll need to target .NET 2.0 or it isn't going to run on 98. Same with Office, pick the lowest version you want to support.
Microsoft has done a terrific job keeping the COM interop for Office backwards compatible, odds are good that a user with a newer version of Office can use your program without problem. This of course is not a guarantee, you need to test it. Which in itself should be a guide to what version of Office you're willing to support. It better be one that you have access to. An MSDN subscription is a good way to get different versions.
Using late binding as suggested by Wiktor is the last thing you want to do. It doesn't stop you from accidentally using an interface that isn't available in an earlier version.
1) take advantage of the dynamic binding
2) stick with late binding
and your code will work on any version.
// work with any version
Type wordType = Type.GetTypeFromProgId( "Word.Application" );
dynamic wordApp = Activator.CreateInstance( wordType );
// late binding + dynamics - always works
wordApp.Visible = true;
