Delegate declaration and instantiation in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a delegate in C#?

A delegate is a type that represents references to methods with a specific parameter list and return type. It allows methods to be passed as parameters or assigned to variables.

beginner

How do you declare a delegate that takes an int and returns void?

You declare it like this:

public delegate void MyDelegate(int number);

beginner

How do you instantiate a delegate to point to a method named 'PrintNumber'?

You instantiate it like this:

MyDelegate d = new MyDelegate(PrintNumber);

or simply

MyDelegate d = PrintNumber;

intermediate

Can a delegate hold references to multiple methods?

Yes, delegates can hold references to multiple methods. This is called a multicast delegate, and it calls all methods in its invocation list when invoked.

beginner

What happens when you invoke a delegate?

When you invoke a delegate, it calls the method(s) it references with the provided arguments, and returns the result if the method has a return type.

How do you declare a delegate that returns an int and takes no parameters?

A delegate void MyDelegate(int);

B public int delegate MyDelegate();

C public delegate int MyDelegate();

D delegate MyDelegate int();

The correct syntax is 'public delegate int MyDelegate();' which declares a delegate returning int and taking no parameters.

Which of the following is a valid way to instantiate a delegate named 'MyDelegate' pointing to method 'Show'?

A MyDelegate d = new MyDelegate(Show);

B MyDelegate d = Show();

C MyDelegate d = delegate Show();

D MyDelegate d = new Show();

You instantiate a delegate by using 'new MyDelegate(MethodName);' or simply 'MyDelegate d = MethodName;'.

What is a multicast delegate?

A A delegate that can reference multiple methods.

B A delegate that returns multiple values.

C A delegate that can only reference one method.

D A delegate that is declared inside a class.

A multicast delegate holds references to multiple methods and calls them all when invoked.

What keyword is used to declare a delegate in C#?

A action

B event

C func

D delegate

The 'delegate' keyword is used to declare a delegate type.

If a delegate references multiple methods, what happens when you invoke it?

A Only the last method is called.

B All referenced methods are called in order.

C Only the first method is called.

D An error occurs.

A multicast delegate calls all methods in its invocation list in order when invoked.

Explain how to declare and instantiate a delegate in C# with an example.

Think about how you define a delegate type and then create an object of that type pointing to a method.

Describe what happens when you invoke a multicast delegate.

Consider how a delegate can hold more than one method and what that means when you call it.