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After a recent Visual Studio update, I am now getting little green dots appearing beneath code, indicating places I could modernise and presumably improve my code to use the latest C# features.

One of these recommends testing for null using the is keyword. Eg.

Don't write...

if( x == null )

Write this instead...

if( x is null )

I'd like to understand the advantage of this and I don't seem to be able to find a simple answer to this anywhere. Anyone?

What I have tried:

I've tried Googling around but don't seem to be able to find a straight answer.
Updated 24-Aug-18 0:25am
Jochen Arndt 24-Aug-18 6:20am
First hit for "c# is null vs == null":

The straight forward answer is in that thread:
There is no difference for this special case (checking for null).
Patrick Skelton 24-Aug-18 7:04am
I think I googled 'what is the advantage of c# is operator'.

There is a detailed blog post that can answer this for you: "is null" versus "== null" in C#[^]
I googled "== null vs is null" and this was the first result

c# - What is the difference between "x is null" and "x == null"? - Stack Overflow[^]

There are many more results if you search yourself.

The main issue seems to be that you can overload "==" to change its behaviour so when you use "== null" you have no guarantee what code is actually being called and how "== null" is being defined. For example if I have a Person class I could overload == for Person to say that if the person has no ID then it is null. When your code uses "if (p == null)" the result might be "true" despite the variable "p" not actually being a null reference.

However when you use "is" that can't be overloaded so checking "is null" gives a more accurate view of if the variable is a null reference or not.

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