Why am I getting "CS0472: The result of the expression is always true since a value of type int is never equal to null of type int?"

Question

string[] arrTopics = {"Health", "Science", "Politics"};

I have an if statement like:

 if (arrTopics.Count() != null)

When I hover my mouse over the above statement, it says:

Warning CS0472: The result of the expression is always true since a value of type int is never equal to null of type int?

I am not able to figure out why it is saying so. Can anybody help me?

Solution 1

int can never be equal to null. int? is the nullable version, which can be equal to null.

You should check if(arrTopics.Count() != 0) instead.

Solution 2

What are you trying to ask here?

   Array.Count() returns an int which will never be null.

If you want to know if the Array has been initialised then:

   if(arrTopics !=null) ...

if you want to know if it's been initialised but has no members then:

  if(arrTopics.Count() > 0) ...

Solution 3

It means what it says.

The "Count" method returns a value type. It's an integer. It will always have a value where it's default value is zero.

Your check really should be:

if (arrTopics.Count() != 0)

Solution 4

null represents the absence of any value, not the number 0. And as the message says an int can never be null since it's neither a reference type nor a nullable value type and thus always has some value.

Solution 5

Like the error says, int can never be null. I'd change the code to

if (arrTopics != null && arrTopics.Any())

Or even more efficient if you know arrTopics is an array and never null is

arrTopics.Length != 0

View more solutions

Comments

[Matt]

Possible duplicate of Why type "int" is never equal to 'null'?

[m.edmondson]

Couldn't have answered better myself. Just to add to this, and int cannot possibly be null as it is a value type not a reference type

[Jon Skeet]

@m.edmondson: But Nullable<int> is a value type and that can have a null value, so your reasoning doesn't work.

[m.edmondson]

@Jon Skeet - Apologies if thats wrong, I was going off what I read in the docs that "Nullable types are instances of the System.Nullable struct."

[Artur Mustafin]

Count() for an array is not a property - it is method

[Jon Skeet]

@m.edmondson: Yes, the Nullable struct. So a reference type. More accurate would be: int cannot possible be null as it is a non-nullable value type, not a reference type or nullable value type.

[Khepri]

Woops, yeah, mistype...my bad. Code said method, comment said property. I've straightened out the mis-alignment.

[Alex Bagnolini]

@Jon: I guess you wanted to write "Yes, the Nullable struct. So a value type"