Why is this an issue?

When declaring a Windows Communication Foundation (WCF) OperationContract method as one-way, that service method won’t return any result, not even an underlying empty confirmation message. These are fire-and-forget methods that are useful in event-like communication. Therefore, specifying a return type has no effect and can confuse readers.

Exceptions

The rule doesn’t report if OperationContractAttribute.AsyncPattern is set to true.

How to fix it

Code examples

Noncompliant code example

<ServiceContract>
Interface IMyService
    <OperationContract(IsOneWay:=True)>
    Function SomethingHappened(ByVal parameter As Integer) As Integer ' Noncompliant
End Interface

Compliant solution

<ServiceContract>
Interface IMyService
    <OperationContract(IsOneWay:=True)>
    Sub SomethingHappened(ByVal parameter As Integer)
End Interface

Resources

Documentation

Microsoft Learn - OperationContractAttribute