DataTypes in C#

DataTypes are the basic building block of any language. Microsoft has tried to standardise the datatypes in .NET framework by introducing a limited, fixed set of types that can be used to represent almost anything in programming world.

C++ was very rich in datatypes, but that leads to confusion too. Especially, when you write components that may be consumed by applications written in other platforms, you have to make sure the types used are compatible with other platforms too!

.NET types start from a clean slate. All .NET languages share the same types. So, they are all compatible and no worries.This means, you can call C# code from VB.NET and vice versa, without worrying about type conversions.

.NET data types are either structures or classes, part of the System namespace. For example, the following data types are implemented as struct in .NET:

Int16

Int32

Double


(String is implemented as a class in .NET, for various reasons.)

If you are not very familiar with struct and class, don't worry about it. You can just use them as if they are simple data types.

Here is how you can declare variables of type Int, Double and String:

Int16 age, employeeNumber;

Double salary;

String name, address;

You can use any of the .NET data types directly in any .NET language - in C#, VB.NET or xyz.NET.But in addition to the .NET types, each language provides a set of primitive types, which map to the corresponding types in .NET class library. This is why you may see some people use string and some others use String. There is no big difference. string is a primitive data type in C# and String is the corresponding class in .NET class library. The string in C# is mapped to the class in .NET class library. So, whether you use string orString,there is no real difference.

DataTypes in C# and the corresponding class/struct in .NET class library

The following list shows the list of data types available in C# and their corresponding class/struct in .NET class library.

C# Data type	Mapped to .NET class/struct
sbyte	System.SByte
byte	System.Byte
char	System.Char
float	System.Single
decimal	System.Decimal
double	System.Double
ushort	System.UInt16
short	System.Int16
uint	System.UInt32
int	System.Int32
ulong	System.UInt64
long	System.Int64
bool	System.Boolean
string	System.String
object	System.Object

Value Types & Reference Types

In C# data types are classified into two :

value types 

reference types

The following tables shows some of the differences between values types and reference types.

value types	reference types
allocated on stack	allocated on heap
a value type variable contains the data itself	reference type variable contains the address of memory location where data is actually stored.
when you copy a value type variable to another one, the actual data is copied and each variable can be independently manipulated.	when copying a reference type variable to another variable, only the memory address is copied. Both variables will still point to thesame memory location, which means, if you change one variable, the value will be changed for the other variable too.
integer, float, boolean, double etc are value types.	string and object are reference types.
struct is value type.	classes and interfaces are reference types.