C # tutorial Operator Overloading

Operator Overloading
C# oprator have some special meaning ,but you can change and redefine operator meaning.

Some Point to remember before define Operator Overloading

• The method should be a public and static method
• The method is marked by keyword "operator" followed by the operator symbol

Below is the example of of unary(+) operator overloading
 
Example 1

using System;

public class Program

{

                  public static void Main()

                  {

                         Area obj1 = new Area(10,10);

                         Area obj2= new Area(15, 12);

                         Area overlod_obj = obj1 + obj2;

                         Console.WriteLine("Value of mX :"+overlod_obj.GetValX().ToString());

                         Console.WriteLine("Value of mY :" + overlod_obj.GetValY().ToString());

                         Console.ReadKey();

                  }

}

class Area

{

            int mX;

            int mY;

            public Area(int x, int y)

            {

                mX = x;

                mY = y;

            }

            public static Area operator +(Area m1, Area m2)

            {

                return new Area(m1.mX * m2.mX, m2.mY * m2.mY);

            }

           public int GetValX()

          {

              return mX;

          }

          public int GetValY()

         {

            return mY;

         }

}

Output :

Value of mX :150
Value of mY :144

Below is the table , showing  Operator,Operator Type and Overloading Possible or not

Operator Type	Operator	Overloading Possible
unary	+, -, !, ~, ++, --	Yes
binary	+, -, *, /, %	Yes
comparison	==, !=, <, >, <=, >=	Yes
conditional	&&, ||	Yes
assignment	+=, -=, *=, /=, %=	No
Misc..	=, ., ?:, ->, new, is, sizeof, typeof	No

Below is the example of of unary(++) operator overloading

Example 2

using System;

public class Program

{

           public static void Main()

           {

     

                 Area obj1 = new Area(10);

                Console.WriteLine("Value of m :" + obj1.GetValueX().ToString());

                Area obj2 = obj1++;

                Console.WriteLine("Value of m :" + obj2.GetValueX().ToString());

               Console.ReadKey();

          }

}

class Area

{

         int m;

        public Area(int x)

         {

             m = x;

        }

         public static Area operator ++(Area obj)

        {

             obj.m++;

             return obj;

        }

        public int GetValueX()

        {

              return m;

        }

}

Output :

Value of m :10
Value of m :11

040 C# Preprocessor Directives

Preprocessor directive
Preprocessor directive gives instruction compiler , before the actual compilation starts.  Preprocessor directives begin with #, but do not ends with semicolon (;) . C and C++  have separate processor, which create macros . C# do not have any separate Preprocessor.  C# considers Preprocessor directive as  instruction.

A simple program with Preprocessor directive

Example  

#define mySysmbol

using System;

public class Program

{

              public static void Main()

               {

                   #if (mySysmbol)

                      Console.WriteLine("mySysmbol is defined");

                  #endif

                 Console.ReadKey();

            }

}

 Output :
mySysmbol is defined

Here is the most common used Preprocessor directive.

directive	What is ?
#define	define symbol Preprocessor. The symbol maybe sequence of character
#undefine	undefine the symbol which was defined by the #define.
#if	test or check particular symbol or symbol with compound statement with operator return true or false. If true is return , some statement is executed
#else	if #if returns false , this code block is executed with some statement
#elif	checking of compound conditional statement on define by the #define
#endif	close or end code block started from #if directives
#line	compiler line number can be customize
#error	customized error , is generated from desired location
#warning	customize warning is generated from desired location
#region	specify an area code blocks. Expand and collapse functionalities is by defauly in .Net framework
#endregion	end code block area define by #define

A Preprocessor directive is defined at the top of a program as it is defined before the compilation of program . Preprocessor directive symbols  and same name variable can be declared, both do not conflict each other.

A simple program with Preprocessor directive , directive symbol and variable are same name.

Example  

#define mySysmbol

using System;

public class Program

{

          public static void Main()

         {

                    string mySysmbol = string.Empty;

                    mySysmbol = "I Am Learning C#";

                   #if (mySysmbol)

                               Console.WriteLine("mySysmbol is defined");

                  #endif

                  Console.ReadKey();

           }

}

Output :
mySysmbol is defined

If you are writing check statement (if) , you can use operator like =, == ,!=,&&,||,! . #region  is generally written when long term code is written , code is  separated  with different part of logic.

A simple program with Preprocessor directive , with operator.

Example

#define mySysmbol1

#define mySysmbol2

using System;

            public class Program

            {

                          public static void Main()

                         {

                                #if (mySysmbol1 && mySysmbol2)

                                {

                                           Console.WriteLine("mySysmbol1 and mySysmbol2 defined");

                                }

                               #endif

                               Console.ReadKey();

                    }

}

Output :
mySysmbol1 and mySysmbol2 defined

045 C# Keywords

Keyword  
C#  keywords  are predefined and reserved for a language usage.Each keyword  have its own meaning and instruction to the compiler. If you use the same name identifier, it will conflict and  throw error. You can use the same name of a keyword  adding @ at the start of a identifier name.

Here  is the example of how error occurred  if we use same name identifier and keyword.
Example 1

using System;

using System.Collections.Generic;

using System.Text;

namespace ConsoleApplication1

{

           class Program

           {

                     static void Main(string[] args)

                   {

                         student case = new student();

                    }

          }

          class student

         {

              string Name;

             int Roll_Number;

          }

}

Output :Error

Invalid expression term 'case'    

Here 'case' is reserve keyword , we used as identifier , causes error.

Here is the example how we can use same name identifier and keyword without error.

Example 1

using System;

using System.Collections.Generic;

using System.Text;

namespace ConsoleApplication1

{

                  class Program

                 {

                        static void Main(string[] args)

                        {

                                   student @case = new student();

                         }

                 }

               class student

               {

                 string Name;

                 int Roll_Number;

             }

}



There are two types of Keyword, reserve and contextual.

 

Here is the list of reserved keyword commonly used.

abstract	explicit	const	event
return	new	override	extern
readonly	sealed	static	unsafe
virtual	volatile	public	private
internal	protected	if	else
switch	case	do	foreach
in	while	break	continue
default	goto	throw	try
catch	finally	unchecked	checked
fixed	lock	ref	out
using	awit	true	enum
void	bull	bite	case
class	decimal	int	double
float	string	unit	sbyte
struc	long	double

Contextual keyword : keyword are valid for certain context only. This keyword are not reserved, are reserved for certain context only.

add	async	await	dynamic
get	global	partial	remove
set	value	var	when
where	yield

Here is the example of contextual keyword , 'global' keyword here used for current context only.

Example 1

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleApplication1

{

          class Program

         {

             static void Main(string[] args)

              {

                        global::System.Console.WriteLine("Your Specific Text");

                         Console.ReadKey();

             }

        }

     class System

     {

      }

}