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What is Delegates in C# and Use of Delegates in C#?

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Here I will explain what is delegates in c#.net with example. Basically delegates in c# are type safe objects which are used to hold reference of one or more methods in c#.net. Delegates concept will match with pointer concept of c language.

Whenever we want to create delegate methods we need to declare with delegate keyword and delegate methods signature should match exactly with the methods which we are going to hold like same return types and same parameters otherwise delegate functionality won’t work if signature not match with methods.

 

Syntax of Delegate & Methods Declaration

public delegate int Delegatmethod(int a,int b);

public class Sampleclass

{

public int Add(int x, int y)

{

return x + y;

}

public int Sub(int x, int y)

{

return x + y;

}

}

 

If you observe above code I declared Delegatmethod method with two parameters which matching with methods declared in Sampleclass class.

 

Complete Example

public delegate int DelegatSample(int a,int b);

public class Sampleclass

{

public int Add(int x, int y)

{

return x + y;

}

public int Sub(int x, int y)

{

return x - y;

}

}

class Program

{

static void Main(string[] args)

{

Sampleclass sc=new Sampleclass();

 

DelegatSample delgate1 = sc.Add;

int i = delgate1(10, 20);

Console.WriteLine(i);

DelegatSample delgate2 = sc.Sub;

int j = delgate2(20, 10);

Console.WriteLine(j);

}

}

Output

Add Result : 30

Sub Result : 10

 

What is the use of Delegates?

 

Suppose if you have multiple methods with same signature (return type & number of parameters) and want to call all the methods with single object then we can go for delegates.

 

Delegates are two types

 

      -   Single Cast Delegates

      -  Multi Cast Delegates

 

Single Cast Delegates

 

Single cast delegate means which hold address of single method like as explained in above example.

 

Multicast Delegates

 

Multi cast delegate is used to hold address of multiple methods in single delegate. To hold multiple addresses with delegate we will use overloaded += operator and if you want remove addresses from delegate we need to use overloaded operator -=

 

Syntax of Multicast Delegate & Method Declaration

public delegate void MultiDelegate(int a,int b);

public class Sampleclass

{

public static void Add(int x, int y)

{

Console.WriteLine("Addition Value: "+(x + y));

}

public static void Sub(int x, int y)

{

Console.WriteLine("Subtraction Value: " + (x - y));

}

public static void Mul(int x, int y)

{

Console.WriteLine("Multiply Value: " + (x * y));

}

}


if you observe above code I declared MultiDelegate method with void return type.

Complete Example

 

 

public delegate void MultiDelegate(int a,int b);

public class Sampleclass

{

public static void Add(int x, int y)

{

Console.WriteLine("Addition Value: "+(x + y));

}

public static void Sub(int x, int y)

{

Console.WriteLine("Subtraction Value: " + (x - y));

}

public static void Mul(int x, int y)

{

Console.WriteLine("Multiply Value: " + (x * y));

}

}

class Program

{

static void Main(string[] args)

{

Sampleclass sc=new Sampleclass();

MultiDelegate del = Sampleclass.Add;

del += Sampleclass.Sub;

del += Sampleclass.Mul;

del(10, 5);

Console.ReadLine();

}

}

 

Output: Whenever we run above code we will get output like as shown below

Addition Value:15

Subtraction Value: 5

Multiply Value:50

posted Jun 2, 2016 by Jdk

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Related Articles

Standard Date and Time Format Specifiers

 A Date and time format specifier is a special character that enables you to display the date and time values in different formats. For example, you can display a date in mm-dd-yyyy format and time in hh:mm format. If you are displaying  GMT time as the output, you can display the GMT time along with the abbreviation GMT using date and time format specifiers.

The date and time format specifiers allow you to display the date and time and time in 12-hour and 24-hour formats.

The following is the syntax for date and time format specifiers.

Console.WriteLine(“{format specifier}”, <datetime object>);

Where,

Format specifier: Is the date and time format specifier.

Datetime object: Is the object of the DateTime class.

Some Standard date and time specifiers are used in the Console.WriteLine() method with the datetime object. To create the datetime object, you must create an object of the DateTime class and initialize it. The formatted date and time are always displayed as string in the console window.
                                                                                                      

 

The table shown below displays some of the standard date and time format specifiers in C#.

Format Specifier

Name

Description

  D

Long date

Displays date in long date pattern. The default format is “dddd*, MMMM*, dd, yyyy”.

  d

Short date

Displays date in short date pattern. The default format is “mm/dd/yyyy”

  f

Full date/time (short time)

Displays date in long date and short time patterns,, separated by a space. The default format is “dddd*”, MMMM* dd, yyyy HH*:mm*”.

  F

Full date/time (long time)

Displays date in long date and long time patterns, separated by a space. The default format is “dddd*, MMMM* dd,,yyyy HH*: mm*: ss*”.

  G

General date/time (short time)

Displays date in short date and short time patterns, separated by a space. The default format is “MM/dd/yyyy  HH*:mm*”.

 

The following snippet demonstrates the conversion of a specified date and time using the d,D,f,F and g date and time format specifiers:-

DateTime dt =  DateTime.Now;

//Returns short date (MM/DD/YYYY)

Console.WriteLine("Short date format (d): {0:d}",dt);

//Returns long date (Day, Month Date, Year)

Console.WriteLine("Long date format (D) : {0:D}", dt);

//Returns full date with time and without seconds

Console.WriteLine("Full date with time without seconds (f) : {0:f}", dt);

//Returns full date with time and with seconds

Console.WriteLine ("Full date with time with seconds (F) : {0:F}", dt);

//Returns short date and short time without seconds

Console.WriteLine ("Short date and short time without seconds (g) : {0:g}", dt);

 

Output:

Short date format (d) : 23/06/2017

Long date format  (D) : Friday, June 23, 2017

Full date with time without seconds (f) : Friday, June 23, 2017 11:12 AM

Full date with time with seconds (F): Friday, June 23, 2017 11:12:34 AM

Short date and short time without seconds (g): 23/06/2017 11:12 AM

 

More Standard Date and Time Format Specifiers

Format Specifier Name   Description
  G General date/time (long time)  Displays date in short date and long time patterns, separated by a space. The default format is "MM/dd/yyyy HH*:mm*:ss*".
 m or M Month day Displays only month and day of the date.The default format is "MMMM* dd".
  tShort time Displays time in short time pattern.The default format is "HH*:mm*".
  TLong time Displays time in long time pattern. The default format is "HH*:mm*:ss*".
 y or YYear month pattern Displays only month and year from the date.he default format is "YYYY MMMM*".
   

 

The following snippet demonstrates the conversion of a specified date and time using the G,m,t,T :-

DateTime dt = DateTime.Now;

//Returns short date and short time with seconds

Console.WriteLine ("Short date and short time with seconds (G) : {0:G}",dt);

//Returns month and day -M can also be used 

Console.WriteLine ("Month and day (m) : {0:m}", dt);

//Returns short time 

Console.WriteLine("Short time (t) : {0:t}", dt);

 

//Returns short time with seconds

Console.WriteLine("Short time with seconds (T) : {0:T}", dt);

//Returns year and month -Y also can be used 

Console.WriteLine ("Year and Month (y): {0:y}" dt);

Output:

Short date and short time with seconds (G): 23/06/2017 11:40:55 AM

Month and day (m) : June 23

Short time (t) : 11:40 AM

Short time with seconds (T): 11:40:55 AM

Year and Month (y): June , 2017 

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