I have got an integer value and i need to check if it is NULL or not. I got it using a null-coalescing operator
C#:
public int? Age;
if ((Age ?? 0)==0)
{
// do somethig
}
Now i have to check in a older application where the declaration part is not in ternary. So, how to achieve this without the null-coalescing operator.
Nullable<T> (or ?) exposes a HasValue flag to denote if a value is set or the item is null.
Also, nullable types support ==:
if (Age == null)
The ?? is the null coalescing operator and doesn't result in a boolean expression, but a value returned:
int i = Age ?? 0;
So for your example:
if (age == null || age == 0)
Or:
if (age.GetValueOrDefault(0) == 0)
Or:
if ((age ?? 0) == 0)
Or ternary:
int i = age.HasValue ? age.Value : 0;
age.GetValueOrDefault() is marginally faster - it completely bypasses the "do I have a value" check, and just returns the value field - which will have defaulted to default(T), aka 0.Several things:
Age is not an integer - it is a nullable integer type. They are not the same. See the documentation for Nullable<T> on MSDN for details.
?? is the null coalesce operator, not the ternary operator (actually called the conditional operator).
To check if a nullable type has a value use HasValue, or check directly against null:
if(Age.HasValue)
{
// Yay, it does!
}
if(Age == null)
{
// It is null :(
}
Simply you can do this:
public void CheckNull(int? item)
{
if (item != null)
{
//Do Something
}
}
Since C# version 9 you can do this:
public void CheckNull(int? item)
{
if (!(item is null))
{
//Do Something
}
}
Or more readable:
public void CheckNull(int? item)
{
if (item is not null)
{
//Do Something
}
}
There is already a correct answer from Adam, but you have another option to refactor your code:
if (Age.GetValueOrDefault() == 0)
{
// it's null or 0
}
Because int is a ValueType then you can use the following code:
if(Age == default(int) || Age == null)
or
if(Age.HasValue && Age != 0) or if (!Age.HasValue || Age == 0)
As stated above, ?? is the null coalescing operator. So the equivalent to
(Age ?? 0) == 0
without using the ?? operator is
(!Age.HasValue) || Age == 0
However, there is no version of .Net that has Nullable< T > but not ??, so your statement,
Now i have to check in a older application where the declaration part is not in ternary.
is doubly invalid.
As of 2022 you can do it like this:
public int? Age;
if (Age is == 0)
{
// do something
}
.ToString() method help you the same
public int? Age;
if (!string.IsNullOrEmpty(Age.ToString()))
{
// do something
}
??a null-coalescing operator.SomeValueType?is a nullable type.int?is not "an integer value". An "integer value" is never null, so the answer is simple: "it isn't". What you have is aNullable<int>, orint?or just "a nullable int".