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

See

• MITRE, CWE-478 - Missing Default Case in Switch Statement