Exception Must Be Thrown

ID

csharp.exception_must_be_thrown

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

CSharp

Tags

exception-handling, reliability

Description

Reports new SomeException(…​) expressions that are constructed but never raised: the allocation is a statement on its own (or evaluated and discarded) without a throw keyword in front of it.

Rationale

Constructing an exception is the diagnostic side of the work — the run-time error is only surfaced by the throw that follows. A bare new InvalidOperationException(…​) statement runs without effect: the program flow continues, the failure goes unreported, and the caller sees normal completion. The pattern almost always comes from a missing throw keyword introduced during a refactor.

public void Validate(string s)
{
    if (string.IsNullOrEmpty(s))
        new ArgumentException("bad input");                   // FLAW — missing throw
    if (s.Length > 100)
    {
        new InvalidOperationException("too long");            // FLAW
    }
}

public void Ok(string s)
{
    if (string.IsNullOrEmpty(s))
        throw new ArgumentException("bad input");             // OK
}

public Exception MakeError(string s) =>
    new InvalidOperationException(s);                          // OK — returned to caller

Remediation

Add the missing throw keyword. If the construction is intentional (for example to populate a logging record or test fixture), assign it to a variable so the intent is explicit.

References