Why string handling matters in C Sharp (C#) - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a string variable named greeting.

C Sharp (C#)

string greeting = [1];

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

A12345

B"Hello, world!"

CHello, world!

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the double quotes around the text.

Using single quotes which are for characters, not strings.

Strings in C# must be enclosed in double quotes. So, "Hello, world!" is the correct way to assign a string.

2fill in blank

medium

Complete the code to get the length of the string stored in name.

C Sharp (C#)

int length = name.[1];

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

ALength

Blength()

Ccount

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using length() with parentheses which causes an error.

Using lowercase 'length' which is not recognized.

In C#, the Length property (capital L) gives the number of characters in a string.

3fill in blank

hard

Fix the error in the code to convert the string input to uppercase.

C Sharp (C#)

string upper = input.[1]();

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

AToUpper

Btoupper

CToLower

Dtouppercase

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase method names which do not exist.

Confusing ToUpper with ToLower.

The correct method to convert a string to uppercase in C# is ToUpper() with capital T and U.

4fill in blank

hard

Fill both blanks to create a substring from index 2 with length 4.

C Sharp (C#)

string part = text.[1](2, [2]);

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

ASubstring

BSubstr

C4

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Substr' which is not a C# method.

Confusing the length argument with the end index.

The Substring method extracts part of a string starting at the given index and for the given length.

5fill in blank

hard

Fill all three blanks to check if the string message contains 'hello' ignoring case.

C Sharp (C#)

bool containsHello = message.[1]("hello", [2].[3]);

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

AContains

BStringComparison

COrdinalIgnoreCase

DEquals

Attempts:

3 left

💡 Hint

Common Mistakes

Using Equals instead of Contains for substring check.

Not passing the StringComparison argument, so case is considered.

The Contains method can take a StringComparison argument to ignore case. Use StringComparison.OrdinalIgnoreCase for case-insensitive check.

Practice

1. Why is it important to use strings properly in C# programs?

easy

A. Because strings let us work with text and communicate with users

B. Because strings make programs run faster than numbers

C. Because strings are only used for storing numbers

D. Because strings cannot be changed once created

Solution

1. Step 1: Understand the role of strings

   Strings store text data, which is essential for showing messages and handling user input.

2. Step 2: Recognize importance in communication

   Proper string handling helps programs communicate clearly with users and manage text data effectively.

3. Final Answer:

   Because strings let us work with text and communicate with users -> Option A

4. Quick Check:

   Strings = Text handling [OK]

Hint: Strings handle text and messages in programs [OK]

Common Mistakes:

• Thinking strings only store numbers
• Believing strings make code faster
• Assuming strings cannot be changed

2. Which of the following is the correct way to declare a string variable in C#?

easy

A. string name = Alice;

B. String name = 'Alice';

C. var name = Alice;

D. string name = "Alice";

Solution

1. Step 1: Check string declaration syntax

   In C#, strings are declared with the keyword string and text is enclosed in double quotes.

2. Step 2: Validate each option

   string name = "Alice"; uses correct syntax: string name = "Alice";. String name = 'Alice'; uses single quotes which are for characters, not strings. var name = Alice; misses quotes around text. string name = Alice; misses quotes around text.

3. Final Answer:

   string name = "Alice"; -> Option D

4. Quick Check:

   Use double quotes for strings [OK]

Hint: Use double quotes and 'string' keyword for text variables [OK]

Common Mistakes:

• Using single quotes for strings
• Forgetting quotes around text
• Using var without quotes

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

string greeting = "Hello";
greeting += ", World!";
Console.WriteLine(greeting);

medium

A. Hello

B. Hello, World!

C. Hello World

D. Error: Cannot add strings

Solution

1. Step 1: Understand string concatenation

   The operator += adds the right string to the existing string variable.

2. Step 2: Trace the code execution

   Initially, greeting is "Hello". After greeting += ", World!";, greeting becomes "Hello, World!".

3. Final Answer:

   Hello, World! -> Option B

4. Quick Check:

   String += adds text [OK]

Hint: += adds text to existing string [OK]

Common Mistakes:

• Thinking += replaces the string
• Ignoring punctuation in concatenation
• Expecting a runtime error

4. Identify the error in this C# code snippet:

string message = 'Welcome';
Console.WriteLine(message);

medium

A. Console.WriteLine cannot print strings

B. Missing semicolon after string declaration

C. Using single quotes for string instead of double quotes

D. Variable name 'message' is invalid

Solution

1. Step 1: Check string literal syntax

   In C#, strings must be enclosed in double quotes, not single quotes.

2. Step 2: Verify other parts

   Semicolon is present, Console.WriteLine can print strings, and variable name is valid.

3. Final Answer:

   Using single quotes for string instead of double quotes -> Option C

4. Quick Check:

   Strings need double quotes [OK]

Hint: Strings use double quotes, chars use single quotes [OK]

Common Mistakes:

• Using single quotes for strings
• Assuming missing semicolon error
• Thinking Console.WriteLine can't print strings

5. You want to create a program that asks the user for their name and then greets them. Which approach best uses string handling to make the code clear and easy to update?

hard

A. Use a string variable to store the name and then print a greeting using that variable

B. Print the greeting directly without storing the name

C. Use integer variables to store the name characters

D. Concatenate numbers instead of strings for the greeting

Solution

1. Step 1: Understand the need for variables

   Storing the user's name in a string variable allows reuse and clearer code.

2. Step 2: Evaluate options for clarity and update ease

   Use a string variable to store the name and then print a greeting using that variable uses a string variable and concatenation for greeting, making code readable and easy to change. Other options misuse data types or skip storing input.

3. Final Answer:

   Use a string variable to store the name and then print a greeting using that variable -> Option A

4. Quick Check:

   Variables make string code clear [OK]

Hint: Store text in variables for clear, flexible code [OK]

Common Mistakes:

• Not using variables for user input
• Using wrong data types for text
• Skipping string concatenation for messages