Predicate delegate type in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a Predicate delegate that checks if a number is positive.

C Sharp (C#)

Predicate<int> isPositive = [1];

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Ax => x > 0

Bx => x == 0

Cx => x < 0

Dx => x != 0

Attempts:

3 left

💡 Hint

Common Mistakes

Using a lambda that checks for zero or negative numbers instead of positive.

Not returning a boolean value.

The Predicate delegate requires a method or lambda that returns true or false. Here, x => x > 0 correctly checks if the number is positive.

2fill in blank

medium

Complete the code to use the Predicate delegate to find if any number in the array is even.

C Sharp (C#)

int[] numbers = {1, 3, 5, 6};
bool hasEven = Array.Exists(numbers, [1]);

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Ax => x % 2 == 1

Bx => x % 2 == 0

Cx => x > 5

Dx => x < 0

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for odd numbers instead of even.

Using conditions unrelated to evenness.

The Array.Exists method uses a Predicate to check if any element matches the condition. x => x % 2 == 0 checks for even numbers.

3fill in blank

hard

Fix the error in the Predicate delegate that checks if a string is empty.

C Sharp (C#)

Predicate<string> isEmpty = s => s.[1] == 0;

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AIsEmpty

BEquals

CEmpty

DLength

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent method IsEmpty.

Trying to call Length as a method instead of a property.

Strings do not have an IsEmpty() method. Instead, checking s.Length == 0 tells if the string is empty. Here, the lambda uses s.Length property.

4fill in blank

hard

Fill both blanks to create a Predicate that checks if a number is between 10 and 20 (inclusive).

C Sharp (C#)

Predicate<int> isBetween = x => x [1] 10 && x [2] 20;

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A>=

B<

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators like < or > only.

Mixing up the order of operators.

The predicate checks if x is greater than or equal to 10 and less than or equal to 20. So the correct operators are >= and <=.

5fill in blank

hard

Fill all three blanks to create a Predicate that checks if a string starts with 'A' and has length greater than 3.

C Sharp (C#)

Predicate<string> check = s => s.[1]("A") && s.[2] [3] 3;

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

AStartsWith

BLength

C>

DContains

Attempts:

3 left

💡 Hint

Common Mistakes

Using Contains instead of StartsWith.

Using incorrect comparison operators for length.

The predicate uses StartsWith("A") to check the first letter, then checks if Length > 3 to ensure the string is longer than 3 characters.