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)]
  int SomethingHappened(int parameter); // Noncompliant
}

Compliant solution

[ServiceContract]
interface IMyService
{
  [OperationContract(IsOneWay = true)]
  void SomethingHappened(int parameter);
}

Resources

Documentation

Microsoft Learn - OperationContractAttribute