Null-conditional operator and !=

Question

With the introduction of Null-Conditional Operators in C#, for the following evaluation,

if (instance != null && instance.Val != 0)

Answer 1

You could make use of null coallescing operator:

instance?.Val ?? 0

When instance is null or instance is not null but Val is, the above expression would evaluate to 0. Otherwise the value of Val would be returned.

Answer 2

With Null-Conditional operator returned value can always be null

if ((instance?.Val ?? 0) != 0)

If instance was null, then instance?.Val will also be null (probably int? in your case). So you should always check for nulls before comparing with anything:

if ((instance?.Val ?? 0) != 0)

This means: If instance?.Val is null (because instance is null) then return 0. Otherwise return instance.Val. Next compare this value with 0 (is not equal to).

Answer 3

if ((instance?.Val).GetValueOrDefault() != 0)  

the ? conditional operator will automatically treat the .Val property as a Nullable.