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Nullable Class

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Definition

Namespace:
System
Assembly:
System.Runtime.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll

Supports a value type that can be assigned null. This class cannot be inherited.

public ref class Nullable abstract sealed
public static class Nullable
[System.Runtime.InteropServices.ComVisible(true)]
public static class Nullable
type Nullable = class
[<System.Runtime.InteropServices.ComVisible(true)>]
type Nullable = class
Public Class Nullable
Inheritance
Object
Nullable
Attributes
ComVisibleAttribute

Remarks

A type is said to be nullable if it can be assigned a value or can be assigned null, which means the type has no value whatsoever. By default, all reference types, such as String, are nullable, but all value types, such as Int32, are not.

In C# and Visual Basic, you mark a value type as nullable by using the ? notation after the value type. For example, int? in C# or Integer? in Visual Basic declares an integer value type that can be assigned null.

The Nullable class provides complementary support for the Nullable<T> structure. The Nullable class supports obtaining the underlying type of a nullable type, and comparison and equality operations on pairs of nullable types whose underlying value type does not support generic comparison and equality operations.

Boxing and Unboxing

When a nullable type is boxed, the common language runtime automatically boxes the underlying value of the Nullable<T> object, not the Nullable<T> object itself. That is, if the HasValue property is true, the contents of the Value property is boxed.

If the HasValue property of a nullable type is false, the result of the boxing operation is null. When the underlying value of a nullable type is unboxed, the common language runtime creates a new Nullable<T> structure initialized to the underlying value.

Methods

Compare<T>(Nullable<T>, Nullable<T>)

Compares the relative values of two Nullable<T> objects.
Equals<T>(Nullable<T>, Nullable<T>)

Indicates whether two specified Nullable<T> objects are equal.
GetUnderlyingType(Type)

Returns the underlying type argument of the specified nullable type.
GetValueRefOrDefaultRef<T>(Nullable<T>)

Retrieves a readonly reference to the location in the Nullable<T> instance where the value is stored.

Applies to

See also