How many ways are there to check if an object is null?

Question

User1884398186 posted

The most traditional way of checking if an object is null is :  if ( object == null)

Can I also use : if ( object is null)? If yes, then which is more efficient OR is there another better way of doing this?

Answer 1

User300685930 posted
In C#, I always use String.IsNullOrEmpty to figure out if a string is empty.  Otherwise, I think == is the best way to do it.

Answer 2

User1884398186 posted

But the String.IsNullOrEmpty is only for 'string'.

I was asking a question about an object, which could be of any type.

For example, if 'employee' was of type 'Employee', then could I use if (employee is null) or if (employee ==  null)  and which one would be the best from performance point of view?

Answer 3

User-1630302068 posted
From a performance point of view neither of them is doing anything which is operationally excessive so they're equivalent in your Big-O analysis.  If you're not doing your Big-O optimization on your algorithms than any performance questions other than DB optimization is simply putting the cart before the horse.

Answer 4

User397347636 posted

You must use "if (object == null)". 

"object is null" won't even compile.  The C# "is" operator is strictly for type checking, not identity comparisons.

 

Answer 5

User1192250343 posted

if (object == null)

will give an error in SonarQube code quality review like 

Change this condition so that it does not always evaluate to 'false'; some subsequent code is never executed.