Built – in Data Types

The build – in data types are aliases of types originally defined in the .NET class library. These types and the corresponding .NET types are below: -
C# Type            .NET Type
bool            System.Boolean
byte            System.Byte
sbyte            System.SByte
char            System.Char
decimal            System.Decimal
double            System.Double
float            System.Single
int            System.Int32
uint            System.UInt32
long            System.Int64
ulong            System.UInt64
object            System.Object
short            System.Int16
ushort            System.UInt16
string            System.String
The word Object is a class in the .NET class library. It represents the root of all types. Needless to say, we can use either the C# type or the .NET type in our code. For example, the following two statements are equivalent; they both declare an integer variable and assign the value 25 to it:
int myInt = 25;
System.Int32 myInt = 25;
The following two statements are also equivalent; both declare a variable of the object type:
object myObject;
System.Object myObject;
All types except the string and object types are called simple data types.