ECMA-334: 11.4.1 Members

Microsoft .NET Framework, ASP.NET, Visual C# (CSharp, C Sharp, C-Sharp) Developer Training, Visual Studio

11.4.1 Members

An instance of a nullable type T? has two public read-only properties:

• A HasValue property of type bool

• A Value property of type T

An instance for which HasValue is true is said to be non-null. A non-null instance contains a known value and Value returns that value.

An instance for which HasValue is false is said to be null. Attempting to read the Value of a null instance causes a System.InvalidOperationException to be thrown.

In addition to the default constructor, every nullable type T? has a public constructor that takes a single argument of type T. Given a value x of type T, a constructor invocation of the form

new T?(x)

creates a non-null instance of T? for which the Value property is x.

It is never necessary to explicitly invoke a nullable type’s constructor, since equivalent functionality is provided as an implicit conversion from T to T?.