Data types

Simple Types

Byte

The byte type has 8 bits and only accepts positive values.
The sbyte type allows negative values (types that can hold the - sign are called signed)
byte (8 bits) = from 0 to 255
sbyte (8 bits) = from -128 to 127

byte myByte = 127;

Integers

short
- has 16 bits
- from -32768 to 32767
ushort
- accepts positive values only
- has 16 bits
- from 0 to 65535
int
- has 32 bits
- from -2147483648 to 2147483647
uint
- accepts positive values only
- has 32 bits
- 0 to 4294967295
long
- has 64 bits
- from -9223372036854775808 to 9223372036854775807
ulong
- accepts positive values only
- has 64 bits
- from 0 to 18446744073709551615

uint age1 = 25;
short age2 = 25;
long age3 = 25;

Real numbers

float
- Can be positive or negative
- Holds at most 32 bits
- from -3.402823e38 to 3.402823e38
- Ex: 23.5 is written as 23.5f
- We must put an f at the end of the value
double
- Can be positive or negative
- Holds at most 64 bits
- from -1.79769313486232e308 to 1.79769313486232e308
- The default type for a decimal value
- Ex: 23.5 is written as 23.5
decimal
- Can be positive or negative
- Holds at most 128 bits
- from 1.0 x 10e-28 to 7.9 x 10e28
- Ex: 23.5 is written as 23.5m
- We must put an m at the end of the value

double salary = 2.500;
var salary = 2.500; // var automatically picks double
float salary = 2.500f;
decimal salary = 2.500m;

Booleans

Stores only true or false
We use the reserved word bool for booleans

bool userRegistered = false;
bool userRegistered = true;
var userRegistered = false; // Already inferred as Boolean

Char

Stores a single character in Unicode format
We use the reserved word char to define the value
A char value is assigned with single quotes
It has 16 bits, which fits any character

char value = 'a';
var value = 'd'; // Already inferred as Char

String

Stores a sequence of characters
Defined by the reserved word string
Its size depends on the length of the string
It is assigned using double quotes

string oneLetter = "C"; // we can use just one letter
string manyLetters = "Characters";
var manyLetters = "1234"; // Already inferred as String

Var

Used in place of a type name
The type is set by the first value assigned and does not change throughout the project
Use var once you are comfortable with the existing types
It is especially useful with complex types, since it avoids repeating long names

// With complex types
IEnumerable<MyComplexType> student = new List<MyComplexType>();
var student = new List<MyComplexType>();

Object

Generic type that accepts any value or object
Use it when you do not know the type of the data or when it can be of several different types
It has no IntelliSense (editor help) because the type is unknown
Avoid using Object unless it is for generic classes or really needed
We use it when we do not want to define an initial value

object quantity; // we can declare it without a value
quantity = 1;
quantity = 2.5; // since it accepts anything, we can change its value and the program will not complain

Nullable Types

Null means the value is empty or nonexistent
It is different from zero or an empty string
Primitive or complex types can receive the null value
The type must be marked as a Nullable Type
We can assign null to an object
We use ? together with the type to make it a Nullable Type
If a null value is dereferenced, the project will throw an error

int? age = null;
byte? value = 123;

Alias

An alias is a nickname that every .NET type has.
All the types shown so far are aliases.
Since C# is Case Sensitive, it does not matter which one we use, but using the aliases is recommended.

Alias	Original Type
string	System.String
int	Int32

Default Values

All C# primitive types come with a default value
They are never initialized as null
If no value is provided, the default value is used

Type	Default Value
int	0
float	0
decimal	0
bool	false
char	‘0’
string	""