O'Reilly logo

C# 4.0 Pocket Reference, 3rd Edition by Joseph Albahari, Ben Albahari

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Type Basics

A type defines the blueprint for a value. A value is a storage location denoted by a variable (if it can change) or a constant (if it cannot). We created a local variable named x in our first program.

All values in C# are an instance of a specific type. The meaning of a value, and the set of possible values a variable can have, is determined by its type. The type of x in our example program is int.

Predefined Type Examples

Predefined types (also called built-in types) are types that are specially supported by the compiler. The int type is a predefined type for representing the set of integers that fit into 32 bits of memory, from ‒231 to 231‒1. We can perform functions such as arithmetic with instances of the int type as follows:

int x = 12 * 30;

Another predefined C# type is string. The string type represents a sequence of characters, such as “.NET” or “http://oreilly.com”. We can work with strings by calling functions on them as follows:

string message = "Hello world";
string upperMessage = message.ToUpper();
Console.WriteLine (upperMessage);      // HELLO WORLD

int x = 2007;
message = message + x.ToString();
Console.WriteLine (message);         // Hello world2007

The predefined bool type has exactly two possible values: true and false. The bool type is commonly used to conditionally branch execution flow with an if statement. For example:

bool simpleVar = false; if (simpleVar) Console.WriteLine ("This will not print"); int x = 5000; bool lessThanAMile = x < 5280; if (lessThanAMile) Console.WriteLine ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required