Object-Oriented Programming with Visual Basic .NET

2.9. System Namespace

Every time you compile anything in Visual Basic, the compiler automatically references two assemblies: mscorlib.dll and Microsoft.VisualBasic.dll. These two components contain the System and Microsoft.VisualBasic namespaces, respectively (a small portion of the System namespace is also contained in System.dll).

The System namespace is the root namespace of primary types in .NET and contains the base data types used by all languages in the framework. When you declare a primitive data type in VB, it is actually mapped to a type defined in this namespace. Table 2-1 provides a list of the types in System and how they relate to Visual Basic.

Table 2-1. Data type mappings from System to VB

System	Visual Basic	Description
Byte	Byte	8-bit unsigned integer
Int16	Short	16-bit signed integer
Int32	Integer	32-bit signed integer
Int64	Long	64-bit signed integer
Single	Single	32-bit floating point
Double	Double	64-bit floating point
Boolean	Boolean	True or False
Char	Char	Unicode character
Decimal	Decimal	96-bit decimal value
String	String	Unicode character string
Object	Object	Base of all objects

How you declare variables in your code doesn't matter. Each represents a functional equivalent:

Dim x As System.Int32
'Is the same as
Dim x As Integer

If you examine Table 2-1 you will see that the Byte is the only unsigned data type supported by VB. All other integer types are signed. The Common Language Specification doesn't support ...