Fix S3264: FP when using add/remove syntax

[Evangelink]

Description

Rule raises FP when using the add/remove syntax of an event.

Repro steps

public class Foo
{
    private EventHandler someEvent;
    public event EventHandler SomeEvent // Noncompliant - should be compliant
    {
        add
        {
            someEvent += value;
        }
        remove
        {
            someEvent -= value;
        }
    }

    public DoRaise()
    {
        someEvent?.Invoke(this, EventArgs.Empty);
    }
}

Expected behavior

Issue not raised because the event is raised using the private handler.

Actual behavior

Issue is raised because we don't use the event Invoke whereas it is impossible to do so.

Known workarounds

None.

Related information

• SonarC# Version 7.0
• Visual Studio Version 2015/2017