Why is this an issue?

When Select Case statements have large sets of multi-line Case clauses, the code becomes hard to read and maintain.

For example, the Cognitive Complexity is going to be particularly high.

In such scenarios, it’s better to refactor the Select Case to only have single-line case clauses.

When all the Case clauses of a Select Case statement are single-line, the readability of the code is not affected.

Exceptions

This rule ignores:

• Select Case statements over Enum arguments
• fall-through cases
• Return and Throw statements in Case clauses

How to fix it

Extract the logic of multi-line Case clauses into separate methods.

Code examples

The examples below use the "Maximum number of case" property set to 4.

Noncompliant code example

Public Function MapChar(ch As Char, value As Integer) As Integer ' Noncompliant
    Select Case ch
        Case "a"c
            Return 1
        Case "b"c
            Return 2
        Case "c"c
            Return 3
        ' ...
        Case "-"c
            If value > 10 Then
                Return 42
            ElseIf value < 5 AndAlso value > 1 Then
                Return 21
            End If
            Return 99
        Case Else
            Return 1000
    End Select
End Function

Compliant solution

Public Function MapChar(ch As Char, value As Integer) As Integer
    Select Case ch
        Case "a"c
            Return 1
        Case "b"c
            Return 2
        Case "c"c
            Return 3
        ' ...
        Case "-"c
            Return HandleDash(value)
        Case Else
            Return 1000
    End Select
End Function

Private Function HandleDash(value As Integer) As Integer
    If value > 10 Then
        Return 42
    ElseIf value < 5 AndAlso value > 1 Then
        Return 21
    End If
    Return 99
End Function

Resources

Documentation

• Sonar - Cognitive Complexity
• Microsoft Learn - Select…​Case Statement