C# Nullable

In C#, nullable types are used to represent value types that can be assigned a value or set to null. This can be useful when you want to indicate that a value is missing or undefined. In this tutorial, we'll cover the following topics related to nullable types in C#:

Using nullable value types
The Nullable<T> structure
The null-coalescing operator
Nullable reference types (C# 8.0 and later)

Let's begin!

Using nullable value types

To create a nullable value type, use the ? modifier on a value type:

int? nullableInt = null;

You can also use the Nullable<T> structure, where T is the underlying value type:

Nullable<int> nullableInt = null;

You can assign a value to a nullable type just like any other value type:

int? nullableInt = 42;

To get the value of a nullable type, use the Value property:

int? nullableInt = 42;
int intValue = nullableInt.Value; // intValue is now 42

To check if a nullable type has a value, use the HasValue property:

int? nullableInt = null;
bool hasValue = nullableInt.HasValue; // hasValue is now false

The Nullable<T> structure

The Nullable<T> structure is a generic structure used to create nullable value types. It provides the following properties:

HasValue: A boolean indicating whether the nullable object has a value.
Value: The value of the nullable object if it has a value; otherwise, it throws an InvalidOperationException.

The null-coalescing operator

The null-coalescing operator (??) is used to provide a default value when a nullable type is null. It returns the left-hand operand if it has a value; otherwise, it returns the right-hand operand:

int? nullableInt = null;
int intValue = nullableInt ?? 0; // intValue is now 0, because nullableInt is null

Nullable reference types (C# 8.0 and later)

Starting with C# 8.0, you can use nullable reference types to indicate that a reference type can be null. By default, reference types are non-nullable, which means they can't be assigned a null value. To create a nullable reference type, use the ? modifier:

string? nullableString = null;

To enable nullable reference types for your project, add the following line to your .csproj file:

<PropertyGroup>
    <Nullable>enable</Nullable>
</PropertyGroup>

That's it! You now have a basic understanding of how to use nullable types in C#. Nullable types provide a way to represent value types that can have a value or be null, making it easier to handle missing or undefined values in your code.

How to use nullable types in C#
Nullable types allow variables to have a value or be null. They are defined by appending ? to the value type.
```
int? nullableInt = null;
```
Nullable value types in C#
Nullable value types extend value types to allow for a null value.
```
int? nullableInt = null;
```
C# nullable types vs. non-nullable types
- Nullable Types:
```
int? nullableInt = null;
```
- Non-Nullable Types:
```
int nonNullableInt = 42;
```
Nullable reference types in C#
Nullable reference types are introduced to help avoid null-reference exceptions. Enable them in your project settings.
```
#nullable enable
string? nullableString = null;
```
Nullable types and database interactions in C#
Nullable types are useful when working with databases where a field can be null.
```
int? databaseValue = ReadFromDatabase();
```
Working with nullables in C# classes
Nullable types can be used as members in classes:
```
class MyClass
{
    public int? NullableInt { get; set; }
}
```
Nullable types and LINQ in C#
Use nullable types with LINQ to handle potential null values from queries:
```
var result = list.Where(item => item?.Value > 5).ToList();
```

Nullable types and conditional statements in C#

Handle nullable types in conditional statements:

int? nullableValue = GetValue();
if (nullableValue.HasValue)
{
    // Process non-null value
}
else
{
    // Handle null case
}

Using Nullable<T> struct in C#

The Nullable<T> struct provides methods for working with nullable types:

int? nullableInt = null;
Nullable<int> anotherNullableInt = Nullable<int>.FromNullable(nullableInt);

C# nullable types in method parameters

Method parameters can be nullable:

void ProcessValue(int? nullableValue)
{
    // Process nullableValue
}

Handling nullables in C# expressions
Handle nullable types in expressions using the null-conditional operator (?.) and null-coalescing operator (??):
```
int? nullableInt = GetNullableValue();
int result = nullableInt?.GetValueOrDefault() ?? 0;
```
Nullable types in C# and the null-coalescing operator
The null-coalescing operator (??) provides a concise way to handle null values:
```
int? nullableInt = GetNullableValue();
int result = nullableInt ?? 0;
```

C# pattern matching with nullable types

Use pattern matching to check for null:

int? nullableInt = GetNullableValue();
if (nullableInt is null)
{
    // Handle null case
}
else
{
    // Process non-null value
}