TypeCasting (or) Type Conversion

Converting From one datatype to another datatype is called as Typecasting (or) Type Conversion.
C#.NET supports 3 types of type casting

1. Implicit Typecasting
2. Explicit Typecasting 
3. Boxing and unboxing

Implicit Typecasting:

Converting from smaller datatype to bigger datatype is called implicit typecasting. Implicit typecasting is controlled by CLR, their is no need to follow any syntax.

Example:

           Void main()

            {

               short sno=20;

               int ino=sno;

               Console.WriteLine("interger number is: "+ ino);

            }

Explicit Typecasting:

Converting from bigger size of datatype to smaller size of datatype is called implicit type casting. Explicit typecasting has to be controlled by programmer and has to follow the syntax.

C#.NET supports Explicit typecasting in 3 ways

1. General style of typecasting(C++ style)
2. Parsing
3. Converting

General style of typecasting:

Syntax: 

             <Todatatype> <To variable>=<Todatatype><fromvariable>;

Example:

             Void Main()

              {

                 int a=22;

                 byte b=(byte)a;

                 Console.WriteLine("b = " + b);

              }

Output:   

            b=22

Disadvantage:

      There is Chance of loosing data.

Parsing:

Every datatype is represented with a predefined class and Parse() is a predefined method, which is member of all datatype classes. Parse method accepts only string value, which converts from string to any another datatype.

Syntax:

         <Todatatype> <To variable>=<Todatatype>.Parse("Value");

    Example:                                       

        int i=int.Parse(Console.ReadLine());

Example program:

               Void Main()

               {

                  Console.WriteLine("Enter ur name");

                  string name=Console.ReadLine();

                  Console.WriteLine("Enter ur age");

                  int age=int.Parse(Console.ReadLine());

                  Console.WriteLine("Enter ur salary");

                  decimal salary=decimal.Parse(Console.ReadLine());

                  Console.WriteLine("Name: " + name+"Age : " + age + "salary : "+ salary);

                }

Disadvantages:

Parse method accepts only string .Using parse method we can convert only string to any other datatype.

Converting:

Converting is a predefined class which contains all the data types conversion methods.Using converting we can convert from any datatype to other datatype.
Syntax:
         <Todatatype> <Tovariable>=convert.<datatype conversion method ("value")>
Example:
          Void Main()
          {
            Console.WriteLine("Enter a number");
            int a=Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Enter a number");
            int b=Convert.ToInt32(Console.ReadLine());
            int c= a+b;
            Convert.WriteLine(c);
          }
Boxing and Unboxing:
Boxing: Converting from value type to reference type is called as boxing.For example converting from int to object.
Syntax:
         <To datatype><To variable> = <To datatype><To variable >
Unboxing: Converting from reference type to value type is called as Unboxing. For example converting from object to int.
Syntax:
         <To datatype><To variable> = <To datatype><To variable >
Example:
          Void Main()
          {
             int i=25;
             object o=i;   //Boxing
             Console.WriteLine("I = " + i);
             int j=(int)o;   //Unboxing
             Console.WriteLine("J = " + j);
           }
Click here for more  : C#.NET Language Basics