9.3 with .Net 4.0

[GeorgeFaraj]

Is there any way to wrap ArcEngine 9.3 components so that they will work with .Net 4.0?  Has anyone had success doing this? Additionally, does anyone know of a way to run multiple versions (say 9.3 and 10.0) on the same machine?

[RichWawrzonek]

You can run multiple versions of ArcGIS on the same physical computer by using a virtual machine. I've been able to this will both VMWare and Oracle Virtual Box, there are free versions of both.

[RichardWatson]

ESRI does not support the 4.0 framework until 10.1.  Even then, they do not require it nor do they check whether or not it is installed.

If you search the forums you can find various posts where people have used the 4.0 framework in earlier versions of ESRI software even though it is not supported.

In version 10, ESRI had a goal of support multiple installs on the same machine but then abandoned that effort leaving only additional complexity.  So, Rich is correct in that your only option here is to use virtual machines.