Why is this an issue?

A typical code smell known as unused function parameters refers to parameters declared in a function but not used anywhere within the function’s body. While this might seem harmless at first glance, it can lead to confusion and potential errors in your code. Disregarding the values passed to such parameters, the function’s behavior will be the same, but the programmer’s intention won’t be clearly expressed anymore. Therefore, removing function parameters that are not being utilized is considered best practice.

This rule raises an issue when a private procedure of a Class, Module or Structure takes a parameter without using it.

Exceptions

This rule doesn’t raise any issue in the following contexts:

• Procedures decorated with attributes.
• Empty procedures.
• Procedures which only throw NotImplementedException.
• Main methods.
• virtual, override procedures.
• Interface implementations.
• Event handlers.

How to fix it

Having unused function parameters in your code can lead to confusion and misunderstanding of a developer’s intention. They reduce code readability and introduce the potential for errors. To avoid these problems, developers should remove unused parameters from function declarations.

Code examples

Noncompliant code example

Private Sub DoSomething(ByVal a As Integer, ByVal b as Integer) ' "b" is unused
    Compute(a)
End Sub

Private Function DoSomething2(ByVal a As Integer, ByVal b As Integer) As Integer ' "a" is unused
    Compute(b)
    Return b
End Function

Compliant solution

Private Sub DoSomething(ByVal a As Integer)
    Compute(a)
End Sub

Private Function DoSomething2(ByVal b As Integer) As Integer
    Compute(b)
    Return b
End Function