Elegant way to do Chained Null Checks

Question

I am using this solution to do a chained null check in my code

Cleaner way to do a null check in C#?

I was just wondering cant we make it like this.

bool returnValue = Helper.IsNull(nullPerson.contact.address.city);

Wouldn't that be even more cleaner ?

I tried writing such a generic function

public static bool IsNull<T>(this T rootObj)
{
  var visitor = new IsNullExpressionVisitor();
  //...
  //...
}

but then I got stuck on how to make expression out of this rootObject.

Answer 1

One way to approach this (although still somewhat clunky) is to use a construct that's sometimes called a "Maybe" monad.

Using that, the code would become something like this (which you may or may not prefer!):

string city = nullPerson.With(x => x.address)
                        .With(x => x.city);

However, rejoice because C# is getting the "Safe Navigation" operator (?.) in the next version*.

With this new ?. operator, the code would look like this:

city = nullPerson?.address?.city;

(*Allegedly...)

Answer 2

After reading many questions trying to solve the same problem, I would go out on a limb and say that there is currently no way to create really elegant chained null check, where elegant would mean not adding indirection to each component of the chain.

Wrapping the chain in a lambda evaluation is perhaps the least terrible way to do it at the time, and it would only work in:

CheckNull<string>(() => nullPerson.contact.address.city);

T CheckNull<T>(Func<T> f) { try { return f(); } catch { return default(T); } }

I'd rather encourage you to try and follow the Law of Demeter that says that your object shouldn't know about the inner workings of the objects it is working with and ask them to return the value any way they want to instead of going down the class tree.