Switch Default First Or Last

ID

csharp.switch_default_first_or_last

Severity

high

Remediation Complexity

medium

Remediation Risk

low

Remediation Effort

medium

Resource

Code Smell

Language

CSharp

Tags

code-style, control-flow, switch

Description

Reports a switch statement whose default section sits between the case sections instead of first or last. A section with stacked labels such as case 3: default: is judged by the position of the whole section.

Rationale

The position of default makes no difference to the compiler, so it exists purely for the reader, who scans the section list from one end looking for the fallback. A default in the middle is routinely skipped during review, and it is usually the fossil of a case that somebody appended after it rather than a deliberate layout choice.

public string Buried(int code)
{
    switch (code)
    {
        case 1:
            return "created";
        default:                      // FLAW — neither first nor last
            return "unknown";
        case 2:
            return "deleted";
    }
}

public string AtTheEnd(int code)
{
    switch (code)
    {
        case 1:
            return "created";
        case 2:
            return "deleted";
        default:                      // OK — last section
            return "unknown";
    }
}

Remediation

Move the default section to the end of the switch, or to the very beginning if the codebase prefers to state the fallback up front. Keep the choice consistent across the project. Since C# forbids implicit fall-through, moving a section never changes behaviour, provided any goto case / goto default jumps keep referring to the same labels.

References