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?开发者_运维知识库

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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.

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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.

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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);

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Not different but I think

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

is clearer.

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My understanding is they are not different. It only matters when you are dealing with value types.

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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.

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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.