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Programming Visual Basic .NET, Second Edition by Jesse Liberty

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VB.NET Types

Visual Basic .NET can (and should) be treated as a strongly typed language. In a strongly typed language you must declare the type of each object you create (e.g., Integer, Decimal, String, Window, Button, etc.) and the compiler will help you prevent bugs by enforcing that only data of the right type is assigned to those objects. You tell the compiler you want Visual Basic .NET to be strongly typed by adding the line:

Option Strict On

to the top of every source code file. While this is optional it is good programming practice, and this book will assume that Option Strict is set On from now on. You can make this the default in Visual Studio .NET (starting in Version 1.1.) by choosing the menu items Tools->Options->Projects->VB Defaults and setting the default to Option Strict On.

The type of an object signals to the compiler the size of that object (e.g., Integer indicates an object of 4 bytes) and its capabilities (e.g., Buttons can be drawn, pressed, and so forth).

Like C++ and Java, Visual Basic .NET divides types into two sets: intrinsic (built-in) types that the language offers and user-defined types that the programmer defines.

Visual Basic .NET also divides the set of types into two other categories: value types and reference types.[3] The principal difference between value and reference types is the manner in which their values are stored in memory. A value type holds its actual value in memory allocated on the stack (or it is allocated as part of a larger ...

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