S1751 — Loops with at most one iteration should be refactored

Why is this an issue?

A loop statement with at most one iteration is equivalent to an If statement; the following block is executed only once.

If the initial intention was to conditionally execute the block only once, an If statement should be used instead. If that was not the initial intention, the block of the loop should be fixed so the block is executed multiple times.

A loop statement with at most one iteration can happen when a statement unconditionally transfers control, such as a jump statement or a throw statement, is misplaced inside the loop block.

This rule raises when the following statements are misplaced:

• Exit
• Continue
• Return
• Throw

How to fix it

Code examples

Noncompliant code example

Public Function Method(items As IEnumerable(Of Object)) As Object
    For i As Integer = 0 To 9
        Console.WriteLine(i)
        Exit For ' Noncompliant: loop only executes once
    Next

    For Each item As Object In items
        Return item ' Noncompliant: loop only executes once
    Next
    Return Nothing
End Function

Compliant solution

Public Function Method(items As IEnumerable(Of Object)) As Object
    For i As Integer = 0 To 9
        Console.WriteLine(i)
    Next

    Dim item = items.FirstOrDefault()
    If item IsNot Nothing Then
        Return item
    End If
    Return Nothing
End Function

Resources

Documentation

• Microsoft Learn - Loop Structures (Visual Basic)
• Microsoft Learn - Exit Statement (Visual Basic)
• Microsoft Learn - Continue Statement (Visual Basic)
• Microsoft Learn - Return Statement (Visual Basic)
• Microsoft Learn - Throw Statement (Visual Basic)
• Microsoft Learn - Throw Statement (Visual Basic)