How to use Nullable variable in C#.
Understand Nullable type in C#
In this article we will learn how to understand Nullable
type in C#. Nullable types are instance of the Nullable structure. If we define
one variable as a Nullable variable then it will capable to store null value
along with its default value.
For example if we define one Boolean variable as Nullable
type then it can store 3 values, they are true, false and null.
Let’s define one Boolean variable and try to assign null
value into it. See in below code.

We are see that compiler is complaining when we are
trying to assign null to normal Boolean variable. So, the solution is we have
to declare the variable as Nullable.

So, now the error has gone because we have defined Boolean variable
as Nullable. Now, let’s check it how it’s
work? We will implement very simple code and will check it within if condition.
public static void Main(String[] args)
{
bool? a = null;
if (a == null)
{
Console.WriteLine("Value is null");
}
else
Console.WriteLine("Value is not null");
Console.ReadLine();
}
Here is sample output.
We can define any variable as Nullable
type. Here is example.
public static void Main(String[] args)
{
bool? a = null;
int? b = null;
float? c = null;
char? d = null;
Console.ReadLine();
}
Here we have defined all primitive
variables as Nullable.
Characteristic and uses of
Nullable type:-
1) Nullable types represent
value-type variable that can be assign the value of null. We cannot define reference
type as Nullable type because by default they accept null.
2) The ability to assign null to
numeric null to numeric and Boolean type is especially useful when we are
dealing with database and other data types that contain elements that may not
be assigned value. For example one Boolean field in database may contain true,
false or null (means not defined).
3) Assigning a value to Nullable type
is just like normal variable. Like int?a =100;
Conclusion:-
In this article we have learned how to use Nullable type in C#. Hope you understood the concept.