Reputation: 16362

check against: null vs default()?

I want to check if a reference type is null. I see two options (_settings is of reference type FooType):

if (_settings == default(FooType)) { ... }

and

if (_settings == null) { ... }

How do these two perform differently?

Upvotes: 37

Answers (7)

Serve Laurijssen

Reputation: 9759

Now that we don't need to pass the type to default anymore, default is preferred.

It is just as readable
It can be used both for value and reference types
It can be used in generics

if (_settings == default) { ... }

Also, after calling

obj = enumerable.FirstOrDefault();

it makes more sense to test for default after that and not for null. Otherwise it should have been FirstOrNull, but value dont have a null value but do have a default.

Upvotes: 21

Stephen Cleary

Reputation: 457137

There's no difference. The default value of any reference type is null.

MSDN's C# reference page for default keyword: https://msdn.microsoft.com/en-us/library/25tdedf5.aspx.

Upvotes: 45

Randolpho

Reputation: 56439

As has been mentioned, there is no difference... but you might want to use default(<type>) anyway, to handle the cases where it's not a reference type. Typically this is only in generics, but it's a good habit to form for the general case.

Upvotes: 2

Jerod Houghtelling

Reputation: 4867

I would definitely go with the specific check against null. Because if the type of the _settings class ever changes you may run into reference issues. At minimum it would require a change to the code breaking the open/close policy.

if( _settings == null ) {...}

This IMO is safer and cleaner.

Upvotes: 3

Andrey

Reputation: 60095

There is no difference, but second one is more readable. The best place to use default is when you deal with generics. Common code is return default(T);

Upvotes: 15