[severos]

I'm writing couple methods that take objects as parameters, currently I'm doing a manual if(obj==null) throw exception/return error. but I've noticed in some built in methods (Encoding.ASCII.GetBytes for example), the parameter have a [NotNull] attribute, any idea how I can get that into my code? tried applying the attribute but can't find it.

[ubbelol]

Not sure about that attribute, but you can do something similar with code contracts:

https://msdn.microsoft.com/en-us/library....110).aspx

[severos]

Not sure about that attribute, but you can do something similar with code contracts:

https://msdn.microsoft.com/en-us/library....110).aspx

A fast reading shows that it's what I want (validate argument isn't null), I'll be taking deeper look at it soon.
Thanks for the help :D

[caesay]

The attributes are merely hints to the caller that the method has a certain requirement (NotNull or CanBeNull). Presumably, these attributes assist Microsoft and the CLR team in enforcing code contracts and doing unit tests.

In C#6 and roslyn i believe these attributes are internal-only, so they've been deprecated.

Some extensions / libraries have their own NotNull attributes - such as Resharper. If you include the JetBrains.Annotations library, you get [notnull] and [canbenull] and many other attributes, and if the consumer of the library has Resharper installed, they will get visual cues if they try to pass in a potential null value as a [NotNull] method parameter.

In summary, these attributes are for code contracts, and are not an excuse to skip doing null checks in your methods.