String interpolation in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the variable name using string interpolation.

C Sharp (C#)

string name = "Alice";
Console.WriteLine($"Hello, [1]!");

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

Aname.ToString()

B"name"

CName

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the variable name in quotes, which prints the word instead of the value.

Using incorrect casing for the variable name.

Using string interpolation, you place the variable name inside curly braces within the string prefixed by $. So, {name} inserts the value of the variable.

2fill in blank

medium

Complete the code to include the variable age in the output string using string interpolation.

C Sharp (C#)

int age = 30;
Console.WriteLine($"You are [1] years old.");

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

Aage

B"age"

CAge

Dage.ToString()

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the variable name, which prints the text instead of the value.

Using incorrect capitalization.

Inside the interpolated string, use {age} to insert the integer variable's value directly.

3fill in blank

hard

Fix the error in the string interpolation to correctly print the full name.

C Sharp (C#)

string firstName = "John";
string lastName = "Doe";
Console.WriteLine($"Full name: [1] {{lastName}}");

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

AfirstName

B"firstName"

CFirstName

DfirstName.ToString()

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the variable name in quotes inside the interpolation.

Using incorrect capitalization of the variable.

Inside the interpolated string, use {firstName} to insert the variable's value. Quotes would print the text literally.

4fill in blank

hard

Fill both blanks to create a greeting with the person's name and age using string interpolation.

C Sharp (C#)

string name = "Emma";
int age = 25;
Console.WriteLine($"Hello, [1]! You are [2] years old.");

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

Aname

Bage

C"age"

D"name"

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around variable names inside the interpolation.

Mixing up the variables or using incorrect casing.

Use {name} and {age} inside the interpolated string to insert the variable values directly.

5fill in blank

hard

Fill all three blanks to print a formatted message with name, age, and city using string interpolation.

C Sharp (C#)

string name = "Liam";
int age = 40;
string city = "Paris";
Console.WriteLine($"Name: [1], Age: [2], City: [3]");

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

Aname

Bage

Ccity

D"city"

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around variable names, which prints the text instead of values.

Incorrect capitalization of variable names.

Inside the interpolated string, use {name}, {age}, and {city} to insert the variable values directly without quotes.

Practice

1. What does string interpolation in C# allow you to do?

easy

A. Use variables only outside of strings

B. Insert variables directly inside a string using { } with a $ prefix

C. Create strings without any variables

D. Concatenate strings using the + operator only

Solution

1. Step 1: Understand string interpolation syntax

   String interpolation uses a $ before the string and curly braces { } to insert variables inside the string.

2. Step 2: Compare options with this syntax

   Only Insert variables directly inside a string using { } with a $ prefix describes inserting variables inside strings using { } with a $ prefix.

3. Final Answer:

   Insert variables directly inside a string using { } with a $ prefix -> Option B

4. Quick Check:

   String interpolation = $ + {variable} [OK]

Hint: Look for $ and { } to spot string interpolation [OK]

Common Mistakes:

• Confusing concatenation (+) with interpolation
• Forgetting the $ before the string
• Using variables outside the string only

2. Which of the following is the correct syntax for string interpolation in C#?

easy

A. string message = $"Hello, {name}!";

B. string message = "Hello, {name}!";

C. string message = $'Hello, {name}!';

D. string message = 'Hello, {name}!';

Solution

1. Step 1: Identify correct string interpolation syntax

   In C#, string interpolation requires a $ before a double-quoted string and variables inside { }.

2. Step 2: Check each option

   string message = $"Hello, {name}!"; uses $ before double quotes and {name} inside, which is correct. The remaining options lack $ or use single quotes which is invalid for interpolation.

3. Final Answer:

   string message = $"Hello, {name}!"; -> Option A

4. Quick Check:

   $ + "string" + {variable} = correct syntax [OK]

Hint: Use $ before double quotes for interpolation [OK]

Common Mistakes:

• Using single quotes instead of double quotes
• Omitting the $ symbol
• Placing variables outside { }

3. What is the output of this C# code?

int apples = 5;
int oranges = 3;
string result = $"I have {apples + oranges} fruits.";
Console.WriteLine(result);

medium

A. I have 8 fruits.

B. I have {apples + oranges} fruits.

C. I have apples + oranges fruits.

D. I have 53 fruits.

Solution

1. Step 1: Evaluate the expression inside the interpolation

   The expression {apples + oranges} adds 5 + 3, which equals 8.

2. Step 2: Substitute the result into the string

   The string becomes "I have 8 fruits." and is printed.

3. Final Answer:

   I have 8 fruits. -> Option A

4. Quick Check:

   Expression inside { } is calculated before output [OK]

Hint: Calculate expressions inside { } before printing [OK]

Common Mistakes:

• Printing the expression text instead of its value
• Concatenating numbers as strings incorrectly
• Ignoring the + operator inside { }

4. Identify the error in this code snippet:

int age = 30;
string message = $"Your age is {age";
Console.WriteLine(message);

medium

A. age variable is not declared

B. Missing $ before the string

C. Missing closing brace } in the interpolation

D. Console.WriteLine is misspelled

Solution

1. Step 1: Check the interpolation braces

   The string has an opening { but no closing } after age, causing a syntax error.

2. Step 2: Verify other parts

   The $ is present, age is declared, and Console.WriteLine is correct.

3. Final Answer:

   Missing closing brace } in the interpolation -> Option C

4. Quick Check:

   Every { must have a matching } [OK]

Hint: Count { and } to avoid missing braces [OK]

Common Mistakes:

• Forgetting to close interpolation braces
• Removing $ accidentally
• Assuming variable is undeclared without checking

5. You want to display a price with two decimal places using string interpolation. Which code correctly formats the price variable?

double price = 12.5;
// Fill in the blank:
string output = $"Price: {___}";
Console.WriteLine(output);

hard

A. price:.2

B. price.ToFixed(2)

C. "{price:2}"

D. price:F2

Solution

1. Step 1: Understand C# string interpolation formatting

   Inside { }, you can add :F2 to format a number with 2 decimals.

2. Step 2: Check each option

   price:F2 uses {price:F2} which is correct. price:.2 is an invalid format specifier (requires :F2 for fixed decimals). price.ToFixed(2) uses ToFixed which is JavaScript, not C#. "{price:2}" is invalid syntax.

3. Final Answer:

   price:F2 -> Option D

4. Quick Check:

   Use :F2 inside { } to format decimals [OK]

Hint: Use :F2 inside { } to show 2 decimals [OK]

Common Mistakes:

• Using JavaScript methods like ToFixed in C#
• Trying to format outside the interpolation braces
• Incorrect format string syntax