Changes in the null conditional operator in C# 6

Question

I am reading up on the changes introduced in C# 6.0 and I have a question about null operators.

In C# 6 this expression

int? x= y?.length;

will be valid if y is null and return a null. No NullargumentException will be raised. Which I believe is a good addition to the language. It removes extra checks and ugly looking code.

But in the case of the null conditional operator we might have code like the following

int? x= y?.length ?? 0;

If y is null then 0 is returned. What happens though if length is null? It returns zero again?

Yes. y?.length is evaluted first. So: when y?.length is null, then (null ?? 0) evalutes to 0. I'm not sure only if cast would bee needed: (int?)0 — pwas
– pwas, Commented Oct 8, 2015 at 12:03
@NikhilAgrawal whe don't know wheter length is int or int?. It looks to me that it is int? rather. — pwas
– pwas, Commented Oct 8, 2015 at 12:04
@nopeflow That's what I was thinking but I was not 100% sure and could not right code to test it as I do nto have c# 6 currently installed — John Demetriou
– John Demetriou, Commented Oct 8, 2015 at 12:05

svick · Accepted Answer · 2015-10-08 15:33:49Z

5

The operator ?? will return the left hand side expression if the expression is not null otherwise the right hand side.

The result type is whatever is on the right side, in your case a int.

y?.length evaluates to null if either y is null, or y.length is null.

In both cases the left hand side of ?? evaluates to null, so 0 is returned by ??.

edited Oct 8, 2015 at 15:33

svick

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answered Oct 8, 2015 at 12:23

thumbmunkeys

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1 Comment

John Demetriou Over a year ago

My speculations are true then :D

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