Why pattern matching matters in C Sharp (C#) - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the object is an integer using pattern matching.

C Sharp (C#)

if (obj is [1] number) {
    Console.WriteLine($"Number is {number}");
}

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

Abool

Bint

Cdouble

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'string' instead of 'int' for integer check.

The is keyword with int pattern checks if obj is an integer and assigns it to number.

2fill in blank

medium

Complete the code to use pattern matching in a switch expression to return a message based on the shape type.

C Sharp (C#)

string message = shape switch {
    Circle c => $"Circle with radius {c.Radius}",
    Rectangle r => $"Rectangle {r.Width}x{r.Height}",
    [1] => "Unknown shape"
};

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

Adefault

Bnull

C_

Dobject

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'default' keyword which is invalid in this context.

The underscore _ is the discard pattern that matches anything not matched before, acting as a default case.

3fill in blank

hard

Fix the error in the pattern matching expression to correctly check if the object is a string with length greater than 5.

C Sharp (C#)

if (obj is string s && s.Length [1] 5) {
    Console.WriteLine("Long string");
}

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

A>

B<

C==

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '==' which do not check for longer strings.

The condition should check if the string length is greater than 5 using the '>' operator.

4fill in blank

hard

Fill both blanks to create a pattern matching expression that checks if the object is a Point with X greater than 0 and Y less than 0.

C Sharp (C#)

if (obj is Point [1] && [1].X > 0 && [1].Y [2] 0) {
    Console.WriteLine("Point in quadrant 4");
}

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

Ap

B>

C<

Dq

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'q' instead of 'p' for the variable name.

Using '>' instead of '<' for Y comparison.

The variable p captures the Point object, and the condition checks if p.X is greater than 0 and p.Y is less than 0.

5fill in blank

hard

Fill all three blanks to create a switch expression that returns the area of shapes, using pattern matching with property patterns.

C Sharp (C#)

double area = shape switch {
    Circle [1] => Math.PI * [2].Radius * [3].Radius,
    Rectangle r => r.Width * r.Height,
    _ => 0
};

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

Ac

Dr

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Using 'r' which is for Rectangle, not Circle.

The variable c captures the Circle object, which is then used to access its Radius property twice to calculate the area.