What minimum version of .NET can I expect on client machines?

Question

I know that in general I can expect .NET 2.0 or better installed on most client/customer machines since it's been included in Windows XP SP1 (SP2?) for some time and comes standard in Vista/2003/2008. But my question now is, can I expect .NET 3.0 to support WCF/WPF? We build component libraries so we can't make too many assumptions and requiring that the our development customers include the 3.0 installer is not ideal.

So the question I guess is, in your experience what is the minimum version of .NET installed on most machines that have .NET installed? Is there a resource that tracks this sort of thing?

To clarify: I do not have any control or influence over the final intstaller. I'm interested in what dependencies are already in place not what to do to bring the client machine up to spec.

Answer 1

In my experience, you can pretty safely assume 2.0 at this point. Assuming versions higher than that always seems to get us into trouble. (On the other hand, just ptoviding a link to the 3.5 installer is pretty easy and painless.)

Answer 2

Never assume anything about a client machine.

It is easy enough to bundle your target framework with the install if the client requires it.

Answer 3

You should implement something like browsercheck on your site to collect all the browser stats. In this way the analytics will speak for itself and there is not need for any assumptions.