Why is "Evaluation of lambda expressions is not valid in the debugger"?

Question

I have a seemingly innocent code snippet, which I typed into Visual Studio 2008 Immediate Window.

? results.Join(lstDocs, Function(docID) docID)
Evaluation of lambda expressions is not valid in the debugger.

As the message says, it's not possible to call a lambda expression in the debugger.
Why is it not allowed?

Answer 1

Here: Why is LINQ absent from debugger windows?

And this previous question: VS debugging “quick watch” tool and lambda expressions

In short, complexity.