How to check if String is null

Question

I am wondering if there is a special method/trick to check if a String object is null. I know about the String.IsNullOrEmpty method but I want to differentiate a null String from an empty String (="").

Should I simply use:

if (s == null) {     // blah blah... } 

...or is there another way?

Answer 1

An object can't be null - the value of an expression can be null. It's worth making the difference clear in your mind. The value of s isn't an object - it's a reference, which is either null or refers to an object.

And yes, you should just use

if (s == null) 

Note that this will still use the overloaded == operator defined in string, but that will do the right thing.

Answer 2

To be sure, you should use a function to check for null and empty as below:

string str = ... if (!String.IsNullOrEmpty(str)) { ... }