IT1811: Delegates and Events

Study Notes

Delegates

A delegate is a class in .NET that encapsulates a method, acting as a reference type data type for method referencing.
Only methods that match the delegate's signature can be called.
Syntax for declaring a delegate includes the delegate keyword, an access modifier, a return type, a delegate name, and parameters in parentheses.
Example declarations:
- public delegate int mathOp(int x, int y);
- public delegate void errorMessage();

Instantiating Delegates

Use the new keyword to create an instance of the delegate that points to a specific method.
Example of instantiation:
- GetAnswer mdAdd = new GetAnswer(Formula.getSum);
- GetAnswer mdAdd = Formula.Addition;

Invoking Delegates

Delegates can invoke referenced methods, requiring matching parameters if referencing a method with a return type.
In classes, after setting up delegate methods and initializing, call the delegate using parentheses to execute.
Example of invoking a method:
- MessageBox.Show(delegateAddition(10,20).ToString());

Generic Delegate Types

Generic delegates are flexible and not restricted to specific data types, capable of referencing methods with varying parameter and return types.
Example declaration of a generic delegate:
- public delegate X DisplayOutput(X arg);
The delegate can point to methods returning type X with a single parameter of type X.

Differences Between Delegates and Interfaces

Delegates serve as safe callback methods without implementation, while interfaces define contracts for classes with specific method signatures.
Both can declare methods, but they differ in usage and execution style, such as handling callbacks versus providing a method framework.

Description

Explore the concept of delegates in .NET with this quiz. Understand how delegates act as class methods encapsulators and their role in event handling. Test your knowledge on declaring and instantiating delegates as per the specifications mentioned in Harwani's work.