Rule S3264: FP when using +=

[costin-zaharia-sonarsource]

Description

Rule S3264: a false positive is raised when chaining events.

Repro steps

namespace TestCases
{
    using System;

    public class EventChainingDirect
    {
        public event EventHandler Logging;

        public void RunTest()
        {
            EventTestBase eventTestBase = new EventTestBase();
            eventTestBase.Logging += Logging;
            eventTestBase.RunSomethingThatSendAnEvent();
        }
    }

    public class EventChainingLambda
    {
        public event EventHandler Logging;

        public void RunTest()
        {
            EventTestBase eventTestBase = new EventTestBase();
            eventTestBase.Logging += (s, e) => Logging(s, e);
            eventTestBase.RunSomethingThatSendAnEvent();
        }
    }

    public class EventTestBase
    {
        public event EventHandler Logging;

        public void RunSomethingThatSendAnEvent() => Logging(this, EventArgs.Empty);
    }
}

Expected behavior

The issue should not be raised in this context.

Actual behavior

EventChainingDirect.Logging is considered non-compliant although the event is invoked by RunSomethingThatSendAnEvent

Known workarounds

Using a lambda function like in EventChainingLambda

Related information

• C#/VB.NET Plugins version: 8.21

[MrDaedra]

We are facing the same issue but not even with direct chaining. For ProcessMessageAsync event we get S3264: Remove the unused event 'ProcessErrorAsync' or invoke it.

internal class ServiceBusMessageProcessor
{
    public event Func<ProcessBrokerMessageEventArgs, Task> ProcessMessageAsync;

    public ServiceBusMessageProcessor(ServiceBusClient serviceBusClient, string topic, string subscriptionName)
    {
        var processor = serviceBusClient.CreateProcessor(topic, subscriptionName, new ServiceBusProcessorOptions());
        processor.ProcessMessageAsync += OnProcessMessageAsync;
    }

    private async Task OnProcessMessageAsync(ProcessMessageEventArgs arg)
    {
        await ProcessMessageAsync?.Invoke(new ProcessServiceBusMessageEventArgs(arg));
    }
}