mshtml 8.0 and Microsoft.mshtml 7.0

I'm a little confuse and maybe you can help me.

I've the mshtml.dll (version 8.0) and the Microsoft.mshtml.dll (version 7.0)

If I go to add a reference to my WPF project and try to add the mshtml.dll, it tells me that the reference has to be a valid assembly or com component. And that's right as I know I have to add a reference to Microsoft.mshtml.d开发者_如何学Cll because it's mshtml.dll's wrapper, am I right?

Now, my mshtml.dll version is 8.0 and Microsoft.mshtml is 7.0.

Where can I found the 8.0 version of Microsoft.mshtml.dll?

If I add the 7.0 of the Microsoft.mshtml.dll it'll run the functions of the mshtml 8 dll?

Why are they different?

Thanks a lot for all, Jayson