null coalescing operator in accessor method

问题

i was looking around in stackoverflow whether putting null coalescing operators within an accessor method has any performance implications.

Before:

private Uri _Url;
public Uri Url
{
    if(_Url == null)
        _Url = new Uri(Utilities.GenerateUri());
    return _Url;
}

After:

private Uri _Url;
public Uri Url 
{
    get 
    {
        return _Url = _Url ?? new Uri(Utilities.GenerateUri());
    }
}

I'm not even sure if the syntax is correct, but when i debug, the private object is set.

Before anyone ask what's the point of doing it, we were debating internally whether to write for readability (the first looks more readable to me), or to write for performance.

I don't know whether the compiler will optimize ?? better than a manual null check all the time. Micro-optimization is bad, but i am just curious

回答1:

You can actually write this as:

return _Url ?? (_Url = new Uri(Utilities.GenerateUri()));

As far as performance goes, it is practically the same thing as using if, so no difference.

来源：https://stackoverflow.com/questions/19534876/null-coalescing-operator-in-accessor-method