using the 'is' keyword in a switch in c#

The latest version of C# (7) now includes this functionality

Type pattern

The type pattern enables concise type evaluation and conversion. When used with the switch statement to perform pattern matching, it tests whether an expression can be converted to a specified type and, if it can be, casts it to a variable of that type. Its syntax is:

   case type varname 

This really looks like a situation for a good polymorphic implementation. If you override the appropriate methods in the derived classes, you may not need the checks in the loop at all.

Nope. See

C# switch statement limitations - why?