String searching and extraction in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find the position of the first occurrence of "cat" in the text.

C Sharp (C#)

string text = "The cat is on the roof.";
int position = text.[1]("cat");
Console.WriteLine(position);

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

AReplace

BContains

CSubstring

DIndexOf

Attempts:

3 left

💡 Hint

Common Mistakes

Using Contains instead of IndexOf returns a boolean, not a position.

The IndexOf method returns the position of the first occurrence of the specified substring.

2fill in blank

medium

Complete the code to extract the substring "dog" from the text.

C Sharp (C#)

string text = "The dog is barking.";
string animal = text.[1](4, 3);
Console.WriteLine(animal);

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AIndexOf

BSubstring

CReplace

DContains

Attempts:

3 left

💡 Hint

Common Mistakes

Using IndexOf returns an integer, not a substring.

Substring(startIndex, length) extracts a part of the string starting at startIndex with the given length.

3fill in blank

hard

Fix the error in the code to check if the text contains the word "bird".

C Sharp (C#)

string text = "A bird is flying.";
bool hasBird = text.[1]("bird");
Console.WriteLine(hasBird);

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AReplace

BIndexOf

CContains

DSubstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using IndexOf returns an integer, which needs comparison to check presence.

Contains returns true if the substring exists in the string, which is suitable for this check.

4fill in blank

hard

Fill both blanks to extract the substring after the first space in the text.

C Sharp (C#)

string text = "Hello World";
int spaceIndex = text.[1](' ');
string afterSpace = text.[2](spaceIndex + 1);
Console.WriteLine(afterSpace);

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AIndexOf

BSubstring

CLastIndexOf

DReplace

Attempts:

3 left

💡 Hint

Common Mistakes

Using LastIndexOf instead of IndexOf finds the last space, not the first.

IndexOf finds the first space position; Substring extracts from that position plus one to the end.

5fill in blank

hard

Fill all three blanks to create a dictionary with words as keys and their lengths as values, only for words longer than 3 characters.

C Sharp (C#)

string[] words = {"apple", "bat", "carrot", "dog"};
var lengths = words.ToDictionary([1] => [1], [2] => [2].Length).Where(kv => kv.Value [3] 3).ToDictionary(kv => kv.Key, kv => kv.Value);
foreach (var item in lengths) Console.WriteLine($"{item.Key}: {item.Value}");

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Aword

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names for key and value selectors causes errors.

Using '<' instead of '>' filters wrong words.

We use 'word' as the key selector and value selector, and filter lengths greater than 3.