The requirement for a final Case Else clause is defensive programming.
This clause should either take appropriate action or contain a suitable comment as to why no action is taken.
Noncompliant code example
Select Case param ' Noncompliant - Case Else clause is missing
Case 0
DoSomething()
Case 1
DoSomethingElse()
End Select
Compliant solution
Select Case param
Case 0
DoSomething()
Case 1
DoSomethingElse()
Case Else ' Compliant
DoSomethingElse()
End Select
