ECMA-334: 12.2 Default values

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

12.2 Default values

The following categories of variables are automatically initialized to their default values:

• Static variables

• Instance variables of class instances

• Array elements

The default value of a variable depends on the type of the variable and is determined as follows:

• For a variable of a value-type, the default value is the same as the value computed by the value-type’s default constructor (§11.1.2).

• For a variable of a reference-type, the default value is null.

[Note: Initialization to default values is typically done by having the memory manager or garbage collector initialize memory to all-bits-zero before it is allocated for use. For this reason, it is convenient to use all-bitszero to represent the null reference. end note]

The default value of a nullable type is an instance for which the HasValue property is false. Referencing the Value property of a default value of a nullable type results in an exception of type System.InvalidOperationException. The default value is also known as the null value of the nullable type. An implicit conversion exists from the null type (§11.2.7) to any nullable type, and this conversion produces the null value of the type.