Delegates in C#- Part 1

Delegates in C#- Part 1

Delegates- (Namespace: System.Delegate)

A beginners guide to delegates with examples

Delegates- (Namespace: System.Delegate)

Definition: *A delegate is a type that safely *encapsulates a method, similar to a function pointer in C and C++. Unlike function pointers, delegates are object-orientedtype-safe and secure. The type of delegate is defined by the name of the delegate.

(The above definition is from** MSDN**.)


A delegate is a reference type that holds the reference to a method or group of methods

Now for a beginner, some of these terminologies might be strange and one might have several questions in one’s mind :

·Question 1- How does one declare and instantiate a delegate?

·Question 2- How does one associate methods to it?

·Question 3- Where are these delegates used in the real world and have I ever come across them knowingly or unknowingly?

Let us get to the first two questions:

Question 1- How does one declare and instantiate a delegate?

Question 2-How does one associate methods to it?

Syntax : delegate

Declaration:- public delegate int MyDelegate (string s);

MyDelegate” here is a delegate which accepts a string as a parameter and returns an integer. The delegate and the methods it wishes to refer must have identical signatures.

Instantiating a delegate & associating one or more methods to it.

A delegate is instantiated by using the new keyword and associated with a method.

Example: public delegate int NumberTailor(int x, int y);

This is how we instantiate it:

var delegate1 = new NumberTailor(DelegateHelpers.AddNumbers);

var delegate2 = new NumberTailor(DelegateHelpers.MultiplyNumbers);

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Function and Delegate Signature should be identical.

We then call the methods:



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Calling of methods via delegate and its output.

As mentioned earlier in the declaration section, a delegate can be used to call any method matching its signature, however, the function must strictly adhere to its signature or else it throws a compilation error (example shown later).

Multicast Delegate

We will now look at an example where we can add references to more than one method to the delegate.

class DelegateHelpers

public static string TamperWithEvidence(string evidence)
var tamperedEvidence = string.Empty;
if (evidence.ToLower().Contains(“evidence”))
tamperedEvidence = evidence.Replace(“evidence”, “***d****”);
return tamperedEvidence;
public static string DoNotTamperWithEvidence(string evidence)
return string.Empty;

The code above is of the two methods we shall refer through our delegate. Notice here, DoNotTamperWithEvidence(string) *method always returns an empty string, whilst *TamperWithEvidence(string) returns a tampered evidence string.

class Program

public delegate string StringTailor(string str);
static void Main(string[] args)
var stringTailor = new StringTailor(DelegateHelpers.TamperWithEvidence);
//stringTailor += DelegateHelpers.DoNotTamperWithEvidence;
var oldString = “The was evidence against him.”;
var newString = stringTailor(oldString);
Console.WriteLine(“old string = “ + oldString
+ “\nnew string = “ + newString

The code above is our main method wherein we call our methods via the delegates. A thing to notice here is that we have commented out the line where we add a new method reference to our delegate. Let us look at the output of the same.

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