Nullable Types in .NET

Example: If you are storing data from a database column and that column can be empty, then you will use a Nullable type.

int? age = null; // This is a Nullable int, which can accept a null value.

using System;

class Program

{

    static void Main()

    {

        int? age = null; // Nullable type

        Console.WriteLine("Age: " + (age.HasValue ? age.Value.ToString() : "No value"));

        age = 30;

        Console.WriteLine("Age: " + age ?? "No value"); // Null Coalescing Operator

    }

}

int? age = null;

double? salary = 50000.50;

Using System.Nullable<T>:

You can also create Nullable types using a generic type.

Nullable<int> age = null;

Nullable<double> salary = 100000.75;

1. HasValue and Value Properties: HasValue: This checks if the Nullable type has a value or not.

Value: This is used to get the value.

int? age = 25;

if (age.HasValue)

{

    Console.WriteLine("Age: " + age.Value);

}

else

{

    Console.WriteLine("Age is null");

}

2. Null Coalescing Operator (??): This operator helps in setting a default value.

int? age = null;

int defaultAge = age ?? 18; // If age is null, then defaultAge will be 18.

Console.WriteLine(defaultAge);

3. Null-Conditional Operator (?.): This operator safely checks if a value is null.

int? age = null;

Console.WriteLine(age?.ToString() ?? "No age available");

Cast and Boxing with Nullable Types

Boxing: When converting a Nullable type to an Object.

int? num = 10;

object obj = num; // Boxing

Console.WriteLine(obj);

Unboxing: Converting from an Object to a Nullable type.

object obj = null;

int? num = (int?)obj; // Unboxing

Console.WriteLine(num);