public class Test
{
    private static ReadOnlyCollection<string>? s_errorPayloadNames;

    private void M(string eventName, string msg)
    {
        var eventCallbackArgs = new EventWrittenEventArgs(this, 0)
        {
            EventName = eventName,
            Message = msg,
            Payload = new ReadOnlyCollection<object?>(new object[] { msg }),
            // Should not warn here
            PayloadNames = s_errorPayloadNames ??= new ReadOnlyCollection<string>(new string[] { "message" })
        };
    }
}