Extension method syntax in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

C Sharp (C#)

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

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

AToUpper

BFirstChar

CLength

DSubstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name that already exists in string like ToUpper.

Not using a descriptive method name.

The method name 'FirstChar' correctly names the extension method that returns the first character of the string.

2fill in blank

medium

Complete the code to declare the extension method inside a static class named StringExtensions.

C Sharp (C#)

public static class [1] {
    public static bool IsNullOrEmpty(this string str) {
        return str == null || str == "";
    }
}

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AStringExtensions

BMyExtensions

CHelper

DExtensions

Attempts:

3 left

💡 Hint

Common Mistakes

Declaring the class as non-static.

Using a different class name than 'StringExtensions'.

Extension methods must be inside a static class. 'StringExtensions' is the correct class name as per the instruction.

3fill in blank

hard

Fix the error in the extension method declaration by completing the method signature correctly.

C Sharp (C#)

public static int WordCount([1] string str) {
    return str.Split(' ').Length;
}

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Apublic

Bstatic

Cthis

Dref

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'static' or 'public' before the parameter instead of 'this'.

Omitting the 'this' keyword.

The 'this' keyword before the first parameter marks it as an extension method parameter.

4fill in blank

hard

Complete the code to create an extension method that returns true if a string contains only digits.

C Sharp (C#)

public static bool [1](this string str) {
    return str.All(c => char.IsDigit(c));
}

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AIsDigitsOnly

B=>

C=>=

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect lambda syntax like '=='.

Choosing a method name that does not describe the functionality.

The method name 'IsDigitsOnly' describes the check. The lambda arrow '=>' is used correctly in the All method.

5fill in blank

hard

Fill all three blanks to create an extension method that returns a dictionary with words as keys and their lengths as values, filtering words longer than 3 characters.

C Sharp (C#)

public static Dictionary<string, int> [1](this string sentence) {
    return sentence.Split(' ').Where([2] => [2].Length > 3).ToDictionary([2] => [2], [3] => [3].Length);
}

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

AWordLengths

Bword

Cw

Dwords

Attempts:

3 left

💡 Hint

Common Mistakes

Using different lambda parameters inconsistently.

Choosing a method name unrelated to word lengths.

The method name 'WordLengths' fits the purpose. The lambda parameter 'w' is used consistently for keys and values.