Sunday, 17 February 2013

Data Type and Type Conversion in C# .NET


Data Type and Type Conversion in C# .NET

 
In this article I will explain about one of the main topics in C# - Data Types. You will also learn about the value and reference types, type conversions and other features related to data types.
         
C# is a strongly typed language; therefore every variable and object must have a declared type.
 
Proper utilization of correct data types allows developers to make the most of the language
 

Data type in C#

 
There are two types of data type in C#:
 
1. built-in data types (Predefine)
2. User Defined data types
 
 built-in data types are further divided as:
 
byte
short
int
float
double
long
char
bool
datetime
string
object
etc
 
User Defined data types are further divided as:
 
class
struct
enum
interface
delegate
array
 
Encoding Scheme  To represent coding scheme.
 
ASCII                8 bits                         28     =      256
 
ANSI                 7 bits                         78     =      128
 
Unicode character sets  16 bits           216    =         65000
 
UTF (Unicode text file) can be:
 
UTF  7
UTF  8
UTF  16
UTF  32
 

Integer Type

 
C# supports eight predefined integer types:
Name
CTS Type
Description
Range
sbyte
System.SByte
8-bit signed integer
-128 to 127 (-27 to 27-1)
short
System.Int16
16-bit signed integer
-32768 to 32767 (-215 to 215-1)
int
System.Int32
32-bit signed integer
-2147483648 to
2147483647 (-231 to 231-1)
long
System.Int64
64-bit signed integer
-9223372036854775808 to
9223372036854775807 (-263 to 263-1)
byte
System.Byte
8-bit unsigned integer
0 to 255 (0 to 28-1)
ushort
System.UInt16
16-bit unsigned integer
0 to 65535 (0 to 216-1)
uint
System. UInt32
32-bit unsigned integer
0 to 4294967295 (0 to 232-1)
ulong
System. UInt64
64-bit unsigned integer
0 to 18446744073709551615 (0 to 264-1)


Floating Point Type

Name
CTS Type
Description
Significant Figures
Range (approx.)
float
System.Single
32-bit single precision floating point
7
plus & minus 1.5 X 10-45 to ±3.4 X 1038
double
System.Double
32-bit single precision floating point
15/16
plus & minus 5.0 X 10-3245 to ±3.4 X 10308

 

Decimal Type

 
Name
CTS Type
Description
Significant Figures
Range (approx.)
decimal
System.Decimal
128-bit high precision decimal notation
28
plus & minus 1.0 X 10-28 to ±7.9 X 1028

 

Boolean Type

 
Name
CTS Type
Values
bool
System.Boolean
true and false

 

Character Type

 
Name
CTS Type
Values
char
System.Char
Represents a single 16-bit (Unicode) character)

 

C# supports two predefined Reference Type

 
Name
CTS Type
Values
object
System.Object
The root type, from which all other types in the CTS derive (including value type)
string
System.String
Unicode character string

 
In .NET Microsoft has divided data types in two parts:
 
1.  Value Type (Fixed in size)
2.  Reference Type (Not fixed in size)
 
In application context, value types are stored in stack but reference types are stored in managed heap.  

Value Type

  • Value types are fixed in size.
  • Value types are made in system stack.
  • Actual values of data are stored in stack.
  • If you assign a value of a variable to another it will create two copies.
All primitive data type except string and object are example of value types.
 
Object is a super type. It can store any type and any size of data. Object is called super type because it helps in inheritance.
 
struct and enum are value type.
 
Note: Stack is an operation entity (LIFO) i.e. it is fixed in size.  

Reference Type 

  • Reference types are not fixed in size.
  • They are maintained in system managed heap but it also uses stack to store reference of heap.
  • Two primitive types (string and object) and non-primitive data types (class, interface & delegate) are examples of reference type.
CLR manages heap (large memory area). Heap address is accessed from stack. In reference type reference is used for processing using both managed heap and stack (operational entity).
 

Type Conversions

 
Conversion is based on type compatibility and data compatibility.
 
There are two types of conversions:
 
1.  Implicit Conversion
2.  Explicit Conversion
 

Implicit Conversion

 
In implicit conversion the compiler will make conversion for us without asking.
 
char -> int -> float is an example of data compatibility.
 
Complier checks for type compatibility at compilation.  
 

Practical demonstration of implicit conversion

 
using System;
 
namespace implicit_conversion
{
    class Program
    {
        static void Main(string[] args)
        {
            int num1 =20000;
            int num2 =50000;
            long total;
            // In this the int values are implicitly converted to long data type;
            //you need not to tell compiler to do the conversion, it automatically does.
            total = num1 + num2;
 
            Console.WriteLine("Total is : " + total);
            Console.ReadLine();
        }
    }
}
 
Below table shows the implicitly type conversions that are supported by C#:
 
From
To
sbyte
short, int, long, float, double, decimal
byte
short, ushort, int, uint, long, ulong, float, double, decimal
short
int, long, float, double, decimal
ushort
int, uint, long, ulong, float, double, decimal
int
long, float, double, decimal
uint
long, ulong, float, double, decimal
long
float, double, decimal
ulong
float, double, decimal
float
double
char
ushort, int, uint, long, ulong, float, double, decimal

 

Explicit Conversion

 
In explicit conversion we specifically ask the compiler to convert the value into another data type.
 
CLR checks for data compatibility at runtime.
 
Explicit conversion is carried out using casts. When we cast one type to another, we deliberately force the compiler to make the transformation.
 
You should never expect that the cast would give you best or correct result. Casts are potentially unsafe. Casting of big data type into small may lead to loosing of data.
 

Practical demonstration of explicit conversion

 
using System;
 
namespace explicit_conversion
{
    class Program
    {
        static void Main(string[] args)
        {
            int num = 65;
           
            char alpha;
            alpha = (char)num;
            // In this the int values are explicitly converted to char data type;
            //you have to tell compiler to do the conversion, it uses casting.
           
            Console.WriteLine("alphabet is: " + alpha);
            Console.ReadLine();
        }
    }
}
 
Note: You can also use Explicit Cast Operator () and unboxing for explicit conversion.
 
Microsoft .NET provides three ways of type conversion:
 
1.  Parsing
2.  Convert Class
3.  Explicit Cast Operator ()
 

Parsing

 
Parsing is used to convert string type data to primitive value type. For this we use parse methods with value types.
 

Practical demonstration of parsing

 
using System;
 
namespace parsing
{
    class Program
    {
        static void Main(string[] args)
        {
            //using parsing
 
            int number;
            float weight;
 
            Console.Write("Enter any number : ");
            number = int.Parse(Console.ReadLine());
 
            Console.Write("Enter your weight : ");
            weight = float.Parse(Console.ReadLine());
 
            Console.WriteLine("You have entered : " + number);
            Console.WriteLine("You weight is : " + weight);
 
            Console.ReadLine();
        }
    }
}
 

Convert Class

 
One primitive type to another primitive type.
 
This class contains different static methods like ToInt32(), ToInt16(), ToString(), ToDateTime() etc used in type conversion.
 

Practical demonstration of Convert class

 
using System;
 
namespace convert_conversion
{
    class Program
    {
        static void Main(string[] args)
        {
            // example of using convert class
 
            string num = "23";
            int number = Convert.ToInt32(num);
 
            int age = 24;
            string vote = Convert.ToString(age);
 
            Console.WriteLine("Your number is : " + number);
            Console.WriteLine("Your voting age is : " + age);
 
            Console.ReadLine();
        }
    }
}
 
Explicit Cast Operator ()
 
In general this operator is used with non-primitive types to up level or down level casting. But it can also used with any type having type compatibility and data type compatibility.
 
using System;
 
namespace explicit_cast_conversion
{
    class Program
    {
        static void Main(string[] args)
        {
            int num1, num2;
            float avg;
            num1 = 10;
            num2 = 21;
            avg = (float)(num1 + num2) / 2;
 
            Console.WriteLine("average is : " + avg);
            Console.ReadLine();
        }
    }
}
 

Boxing and unboxing

 
Boxing and unboxing is an important concept in C# type system. With Boxing and unboxing one can link between value-types and reference-types by allowing any value of a value-type to be converted to and from type object.
 
Boxing  
  • Boxing is a mechanism in which value type is converted into reference type.
  • It is implicit conversion process in which object type (super type) is used.
  • In this process type and value both are stored in object type
Unboxing  
  • Unboxing is a mechanism in which reference type is converted into value.
  • It is explicit conversion process.
Program to show boxing and unboxing:
 
using System;
 
namespace boxing
{
    class Program
    {
        static void Main(string[] args)
        {
            int i = 10;
            object o = i;             // boxing
            int j = (int)o;          // unboxing
 
            Console.WriteLine("value of o object : " + o);
            Console.WriteLine("Value of j : " + j);
 
            Console.ReadLine();
        }
    }
}


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