Factoryless.cs

private static Thing MakeThing(string thingName, int thingVal, string thirdParam)
{
    if (thingName == null)
        throw new ArgumentNullException(nameof(thingName));
    if (thirdParam == null)
        throw new ArgumentNullException(nameof(thirdParam));
        
    return new Thing(thingName, thingVal, thirdParam);
}