Extension methods for built-in types in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an extension method for the string type that returns the first character.

C Sharp (C#)

public static class StringExtensions {
    public static char [1](this string str) {
        return str[0];
    }
}

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

AFirstChar

BFirst

CGetFirst

DCharAt

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that does not clearly indicate it returns the first character.

Forgetting to make the method static or the class static.

The method name 'First' is a common and clear name for returning the first character of a string.

2fill in blank

medium

Complete the code to call the extension method 'IsEven' on an integer variable.

C Sharp (C#)

int number = 4;
bool result = number.[1]();

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AIsEven

BCheckEven

CEvenCheck

DIsOdd

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong method name that does not exist.

Calling a method that checks for odd instead of even.

The extension method is named 'IsEven', so calling number.IsEven() is correct.

3fill in blank

hard

Fix the error in the extension method declaration by completing the code.

C Sharp (C#)

public static class IntExtensions {
    public static bool [1](this int value) {
        return value % 2 == 0;
    }
}

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

ACheckEven

BIsOdd

CIsEven

DEven

Attempts:

3 left

💡 Hint

Common Mistakes

Naming the method 'IsOdd' which contradicts the logic.

Using a vague or unclear method name.

The method name 'IsEven' matches the logic that returns true if the number is even.

4fill in blank

hard

Fill both blanks to create an extension method that returns the last character of a string.

C Sharp (C#)

public static class StringHelpers {
    public static char [1](this string str) {
        return str[2];
    }
}

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

ALastChar

BLength - 1

C[str.Length - 1]

DLast

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect indexing syntax.

Choosing a method name that does not match the functionality.

The method name 'LastChar' clearly describes the purpose, and accessing str[str.Length - 1] returns the last character.

5fill in blank

hard

Fill all three blanks to create an extension method that repeats a string n times.

C Sharp (C#)

public static class StringExtensions {
    public static string [1](this string str, int [2]) {
        return string.Concat(Enumerable.[3](str, [2]));
    }
}

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

ARepeat

Bcount

Dtimes

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names.

Using wrong method names or missing the Enumerable.Repeat call.

The method name 'Repeat' describes the action, 'count' is a common parameter name for number of repetitions, and Enumerable.Repeat is the correct method to repeat a string.