Relational patterns in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the number is greater than 10 using a relational pattern.

C Sharp (C#)

if (number is > [1]) {
    Console.WriteLine("Number is greater than 10");
}

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

A5

B10

C15

D20

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong number to compare.

Using a less than operator instead of greater than.

The relational pattern is > 10 checks if number is greater than 10.

2fill in blank

medium

Complete the code to check if the age is less than or equal to 18 using a relational pattern.

C Sharp (C#)

if (age is [1] 18) {
    Console.WriteLine("Minor age");
}

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

A<=

B>

C<

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using greater than or less than without equal.

Swapping the operator direction.

The pattern is <= 18 checks if age is less than or equal to 18.

3fill in blank

hard

Fix the error in the relational pattern to check if temperature is not equal to 0.

C Sharp (C#)

if (temperature is not [1]) {
    Console.WriteLine("Temperature is not zero");
}

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

A==

B<

C>

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' inside 'is not' which is incorrect.

Using less than or greater than operators.

The correct pattern to check 'not equal' is is not 0.

4fill in blank

hard

Fill both blanks to check if score is between 50 and 100 inclusive using relational patterns.

C Sharp (C#)

if (score is >= [1] and <= [2]) {
    Console.WriteLine("Score is in the passing range");
}

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

A50

B40

C100

D110

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong boundary numbers.

Swapping the lower and upper bounds.

The pattern checks if score is greater than or equal to 50 and less than or equal to 100.

5fill in blank

hard

Fill all three blanks to create a pattern that checks if value is greater than 0, less than 10, and not equal to 5.

C Sharp (C#)

if (value is > [1] and < [2] and not [3]) {
    Console.WriteLine("Value is valid");
}

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

A0

B10

Cis

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'is' instead of 5 for not equal.

Mixing up the boundary numbers.

The pattern checks if value is greater than 0, less than 10, and not equal to 5 using relational patterns.

Practice

1. What does the relational pattern is > 10 check in C#?

easy

A. If a value is greater than 10

B. If a value is equal to 10

C. If a value is less than 10

D. If a value is not equal to 10

Solution

1. Step 1: Understand the relational pattern syntax

   The pattern is > 10 checks if a value is greater than 10.

2. Step 2: Compare with other options

   Options A, B, and D check less than, equality, or inequality, which are different from > 10.

3. Final Answer:

   If a value is greater than 10 -> Option A

4. Quick Check:

   Relational pattern is > 10 means greater than 10 [OK]

Hint: Relational patterns use normal math signs like >, <, == [OK]

Common Mistakes:

• Confusing > with >= or ==.
• Thinking it checks equality instead of comparison.
• Mixing up less than and greater than signs.

2. Which of the following is the correct syntax to check if an integer n is less than or equal to 5 using a relational pattern?

easy

A. if (n is <= 5) { }

B. if (n <= 5) { }

C. if (n is < = 5) { }

D. if (n is <=5) { }

Solution

1. Step 1: Identify correct relational pattern syntax

   The relational pattern syntax uses is followed by the operator and value without spaces inside the operator, like is <= 5.

2. Step 2: Check each option

   if (n is <= 5) { } uses correct syntax: if (n is <= 5). if (n <= 5) { } is normal comparison, not a relational pattern. if (n is < = 5) { } has a space between < and = which is invalid. if (n is <=5) { } misses a space after is, which is required.

3. Final Answer:

   if (n is <= 5) { } -> Option A

4. Quick Check:

   Relational pattern syntax: is <= value [OK]

Hint: Relational patterns need 'is' then operator with no spaces inside operator [OK]

Common Mistakes:

• Using normal comparison without 'is'.
• Adding spaces inside the operator like '< ='.
• Omitting space after 'is'.

3. What will be the output of this C# code?

int x = 7;
if (x is >= 5 and < 10)
    Console.WriteLine("In range");
else
    Console.WriteLine("Out of range");

medium

A. No output

B. Out of range

C. In range

D. Compilation error

Solution

1. Step 1: Evaluate the relational pattern condition

   The condition x is >= 5 and < 10 checks if x is between 5 and 9 inclusive. Since x = 7, it satisfies both parts.

2. Step 2: Determine which branch runs

   Because the condition is true, the Console.WriteLine("In range") runs, printing "In range".

3. Final Answer:

   In range -> Option C

4. Quick Check:

   7 is between 5 and 10, so output is "In range" [OK]

Hint: Check both parts of 'and' relational pattern carefully [OK]

Common Mistakes:

• Thinking 'and' means 'or'.
• Ignoring one part of the condition.
• Assuming syntax error due to 'and'.

4. Identify the error in this code snippet using relational patterns:

int score = 85;
switch (score)
{
    case is > 90:
        Console.WriteLine("Excellent");
        break;
    case is >= 80 and < 90:
        Console.WriteLine("Good");
        break;
    default:
        Console.WriteLine("Average");
        break;
}

medium

A. The 'and' keyword is not allowed in switch case patterns

B. Missing braces around case blocks

C. Relational patterns cannot be used in switch cases

D. The pattern 'is > 90' should be 'case > 90:' without 'is'

Solution

1. Step 1: Identify the syntax error in switch case patterns

   Relational patterns in switch statements use syntax like case > 90:, without the is keyword. The code incorrectly uses case is > 90: and case is >= 80 and < 90:.

2. Step 2: Evaluate the options

   The 'and' keyword is not allowed in switch case patterns is incorrect; and is allowed to combine patterns like case >= 80 and < 90:. The pattern 'is > 90' should be 'case > 90:' without 'is' correctly identifies the misuse of is. Relational patterns cannot be used in switch cases is false; relational patterns are supported in switch cases. Missing braces around case blocks is wrong; braces are not required around case contents.

3. Final Answer:

   The pattern 'is > 90' should be 'case > 90:' without 'is' -> Option D

4. Quick Check:

   Switch case relational pattern: case > value, no is [OK]

Hint: No 'is' keyword needed for relational patterns in switch cases [OK]

Common Mistakes:

• Adding 'is' before relational operators in switch cases.
• Thinking 'and' cannot combine patterns in switch cases.
• Confusing switch statements with 'is' patterns.

5. You want to write a method that returns "Child", "Teen", or "Adult" based on age using relational patterns. Which of these switch expressions correctly implements this?

string GetAgeGroup(int age) => age switch
{
    < 13 => "Child",
    >= 13 and < 20 => "Teen",
    _ => "Adult"
};

hard

A. Replace 'and' with '&&' in the second pattern

B. Correct as is

C. Use nested if statements instead of switch

D. Add parentheses around '>= 13 and < 20'

Solution

1. Step 1: Analyze the switch expression with relational patterns

   The switch expression uses relational patterns correctly: < 13 for "Child", combined pattern >= 13 and < 20 for "Teen", and default for "Adult".

2. Step 2: Confirm syntax correctness

   The 'and' keyword is valid in switch expressions for combining patterns. No parentheses or '&&' are needed here.

3. Final Answer:

   Correct as is -> Option B

4. Quick Check:

   Switch expressions support 'and' for combined relational patterns [OK]

Hint: Use 'and' to combine relational patterns in switch expressions [OK]

Common Mistakes:

• Replacing 'and' with '&&' which is invalid in patterns.
• Adding unnecessary parentheses.
• Thinking switch expressions don't support relational patterns.