Delegates as callback pattern in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a delegate named Callback that takes no parameters and returns void.

C Sharp (C#)

public delegate [1] Callback();

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Astring

Bvoid

Cint

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using a return type other than void when the callback does not return a value.

The delegate must return void because it represents a callback with no return value.

2fill in blank

medium

Complete the code to declare a method named Process that accepts a Callback delegate as a parameter.

C Sharp (C#)

public void Process([1] callback) { callback(); }

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Aint

Bstring

CCallback

DAction

Attempts:

3 left

💡 Hint

Common Mistakes

Using a type like int or string instead of the delegate type.

The method parameter must be of type Callback to accept the delegate.

3fill in blank

hard

Fix the error in the code by completing the delegate invocation inside the Process method.

C Sharp (C#)

public void Process(Callback callback) { callback[1]; }

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A()

B;

C{}

D[]

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to add parentheses when calling the delegate.

Delegates are invoked like methods, so parentheses () are needed to call the delegate.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps strings to their lengths only if length is greater than 3.

C Sharp (C#)

var lengths = new Dictionary<string, int> { { [1], [2] } };

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A"apple"

B"banana"

C"pear"

D"kiwi"

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid syntax for dictionary initialization.

This task is a trick question to check understanding of dictionary initialization syntax. The correct answer is to fill the blanks with key and value strings.

5fill in blank

hard

Fill all three blanks to define and use a delegate as a callback that prints a message.

C Sharp (C#)

public delegate void [1]();

public void Run([2] callback) {
    callback[3];
}

Drag options to blanks, or click blank then click option'

ACallback

C()

DAction

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for delegate and parameter.

Forgetting parentheses when invoking the delegate.

The delegate is named Callback, the parameter type is Callback, and the delegate is invoked with parentheses ().