Data Types

In C#, variables are categorized into the following types:

Value types

Reference types

Pointer types

Value Types
Value type variables can be assigned a value directly. They are derived from the class System.ValueType.

The value types directly contain data. Some examples are int, char, float, which stores numbers, alphabets and floating point numbers respectively. When you declare an int type, the system allocates memory to store the value.

The following table lists the available value types in C# 2010:

Type Represents Range Default
Value
bool Boolean value True or False False
byte 8-bit unsigned integer 0 to 255 0
char 16-bit Unicode character U +0000 to U +ffff '\0'
decimal 128-bit precise decimal values with 28-29 significant digits (-7.9 x 1028 to 7.9 x 1028) / 100 to 28 0.0M
double 64-bit double-precision floating point type (+/-)5.0 x 10-324 to (+/-)1.7 x 10308 0.0D
float 32-bit single-precision floating point type -3.4 x 1038 to + 3.4 x 1038 0.0F
int 32-bit signed integer type -2,147,483,648 to 2,147,483,647 0
long 64-bit signed integer type -923,372,036,854,775,808 to 9,223,372,036,854,775,807 0L
sbyte 8-bit signed integer type -128 to 127 0
short 16-bit signed integer type -32,768 to 32,767 0
uint 32-bit signed integer type 0 to 4,294,967,295 0
ulong 64-bit signed integer type 0 to 18,446,744,073,709,551,615 0
ushort 16-bit signed integer type 0 to 65,535 0
To get the exact size of a type or a variable on a particular platform, you can use the sizeof method. The expression sizeof(type) yields the storage size of the object or type in bytes. Following is an example to get the size of int type on any machine:

namespace DataTypeApplication
{
   class Program
   {
      static void Main(string[] args)
      {
         Console.WriteLine("Size of int: {0}", sizeof(int));
         Console.ReadLine();
      }
   }
}
When the above code is compiled and executed, it produces following result:

Size of int: 4
Reference Types
The reference types do not contain the actual data stored in a variable, but they contain a reference to the variables.

In other words, they refer to a memory location. Using more than one variable, the reference types can refer to a memory location. If the data in the memory location is changed by one of the variables, the other variable automatically reflects this change in value. Example of built in reference types are: object, dynamic and string.

OBJECT TYPE
The Object Type is the ultimate base class for all data types in C# Common Type System(CTS). Object is an alias for System.Object class. So object types can be assigned values of any other types, value types, reference types, predefined or user-defined types. However, before assigning values, it needs type conversion.

When a value type is converted to object type, it is called boxing and on the other hand, when an object type is converted to a value type it is called unboxing.

object obj;
obj = 100; // this is boxing
DYNAMIC TYPE
You can store any type of value in the dynamic data type variable. Type checking for these types of variables takes place at runtime.

Syntax for declaring a dynamic type is:

dynamic <variable_name> = value;
For example,

dynamic d = 20;
Dynamic types are similar to object types except that, type checking for object type variables takes place at compile time, whereas that for the dynamic type variables take place at run time.

STRING TYPE
The String Type allows you to assign any string values to a variable. The string type is an alias for the System.String class. It is derived from object type. The value for a string type can be assigned using string literals in two forms: quoted and @quoted.

For example,

String str = "Tutorials Point";
A @quoted string literal looks like:

@"Tutorials Point";
The user defined reference types are: class, interface, or delegate. We will discuss these types in later chapter.

Pointer Types
Pointer type variables store the memory address of another type. Pointers in C# have the same capabilities as in C or C++.

Syntax for declaring a pointer type is:

type* identifier;
For example,

char* cptr;
int* iptr;
We will discuss pointer types in the chapter 'Unsafe Codes'.