How many runtimes (CLRs) can be loaded in a single process?

Question

I attended Virtual Tech Days today. In Quiz section there was the following question.

"In the previous versions of .NET (before 4.0) how many runtimes (CLRs) can be loaded in a single process?"

Any ideas?

Answer 1

Prior to 4.0 it was only possible to load 2 CLR's into a single process. That is you could load 2.0 SP1 and the Silverlight CLR into the same process. This is a rare case though and I don't know of many cases (any) where this was used.

After 4.0 though, it's possible to have any combination of the following CLR instances in the same process.

• 2.0SP1 and higher
• Silverlight 2.0 and higher
• 4.0 and higher

I am unsure about the state of Silverlight 1.0 (couldn't find a quick reference). I'm fairly certain it does not have this capability though