Top-level statements in modern C# - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print "Hello, World!" using top-level statements.

C Sharp (C#)

Console.[1]("Hello, World!");

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

AWriteLine

BPrint

CDisplay

DOutput

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like Print or Display which do not exist in Console.

Forgetting the parentheses after the method name.

The Console.WriteLine method prints text to the console with a new line.

2fill in blank

medium

Complete the code to declare a variable and print its value using top-level statements.

C Sharp (C#)

int number = 5;
Console.[1](number);

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

APrint

BShow

CDisplay

DWriteLine

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods that do not exist in Console like Print or Show.

Trying to print without parentheses.

Console.WriteLine prints the value of the variable to the console.

3fill in blank

hard

Fix the error in the top-level statement that tries to read input from the user.

C Sharp (C#)

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

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

ARead

BReadLine

CInput

DGetLine

Attempts:

3 left

💡 Hint

Common Mistakes

Using Console.Read which reads a single character code.

Using non-existent methods like Input or GetLine.

Console.ReadLine() reads a full line of input from the user as a string.

4fill in blank

hard

Fill both blanks to declare a variable and print a message using top-level statements.

C Sharp (C#)

var [1] = "C#";
Console.[2]($"Learning [1] is fun!");

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

Alanguage

BWriteLine

CPrint

Dcode

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid variable names.

Using Console.Print which does not exist.

The variable language holds the string, and Console.WriteLine prints the message.

5fill in blank

hard

Fill all three blanks to declare two variables and print their sum using top-level statements.

C Sharp (C#)

int [1] = 10;
int [2] = 20;
Console.[3]([1] + [2]);

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

Aa

Bb

CWriteLine

DPrint

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid method names like Print.

Using variable names that are not consistent.

Variables a and b hold numbers, and Console.WriteLine prints their sum.

Practice

1. What is the main benefit of using top-level statements in modern C#?

easy

A. It only works for console applications with multiple classes.

B. You must always define a Main method to run the program.

C. It requires more boilerplate code than traditional C# programs.

D. You can write code without explicitly defining a class or Main method.

Solution

1. Step 1: Understand top-level statements purpose

   Top-level statements allow writing code directly without wrapping it inside a class or Main method.

2. Step 2: Compare options with this feature

   You can write code without explicitly defining a class or Main method. correctly states this benefit, while others contradict it or add incorrect restrictions.

3. Final Answer:

   You can write code without explicitly defining a class or Main method. -> Option D

4. Quick Check:

   Top-level statements remove boilerplate = A [OK]

Hint: Top-level means no class or Main method needed [OK]

Common Mistakes:

• Thinking Main method is still required
• Believing top-level statements add more code
• Assuming it only works for complex apps

2. Which of the following is the correct way to write a top-level statement program that prints "Hello, World!"?

easy

A. Console.WriteLine("Hello, World!");

B. public static void Main() { Console.WriteLine("Hello, World!"); }

C. class Program { static void Main() { Console.WriteLine("Hello, World!"); } }

D. void Main() { Console.WriteLine("Hello, World!"); }

Solution

1. Step 1: Identify top-level statement syntax

   Top-level statements allow writing code directly without class or method wrappers.

2. Step 2: Check each option

   Console.WriteLine("Hello, World!"); is direct code printing the message, valid as a top-level statement. Others require class or method definitions.

3. Final Answer:

   Console.WriteLine("Hello, World!"); -> Option A

4. Quick Check:

   Direct code without class = C [OK]

Hint: Top-level means just write code directly, no class needed [OK]

Common Mistakes:

• Adding class or Main method unnecessarily
• Using incorrect method signatures
• Forgetting to call Console.WriteLine properly

3. What will be the output of this C# program using top-level statements?

int x = 5;
int y = 10;
Console.WriteLine(x + y);

medium

A. Compilation error

B. 15

C. x + y

D. 510

Solution

1. Step 1: Understand variable initialization and addition

   Variables x and y are integers with values 5 and 10. Adding them gives 15.

2. Step 2: Check Console.WriteLine output

   Console.WriteLine prints the sum of x and y, which is 15, not concatenation or error.

3. Final Answer:

   15 -> Option B

4. Quick Check:

   5 + 10 = 15 [OK]

Hint: Adding integers prints sum, not concatenation [OK]

Common Mistakes:

• Thinking integers concatenate as strings
• Expecting variable names printed
• Assuming top-level causes errors

4. Identify the error in this top-level statement C# code:

int number = 10
Console.WriteLine(number);

medium

A. Missing semicolon after variable declaration.

B. Cannot declare variables in top-level statements.

C. Console.WriteLine is not allowed in top-level statements.

D. Variable 'number' must be declared inside a method.

Solution

1. Step 1: Check syntax of variable declaration

   The line 'int number = 10' is missing a semicolon at the end, which is required in C#.

2. Step 2: Verify top-level statement rules

   Variables can be declared and Console.WriteLine used directly in top-level statements, so other options are incorrect.

3. Final Answer:

   Missing semicolon after variable declaration. -> Option A

4. Quick Check:

   Every statement needs semicolon [OK]

Hint: Check for missing semicolons in statements [OK]

Common Mistakes:

• Thinking variables can't be declared top-level
• Assuming Console.WriteLine is disallowed
• Forgetting semicolon ends statements

5. You want to write a simple C# program using top-level statements that reads a number from the user, doubles it, and prints the result. Which code snippet correctly does this?

hard

A. class Program {
static void Main() {
Console.WriteLine("Enter a number:");
int num = int.Parse(Console.ReadLine());
Console.WriteLine(num * 2);
}
}

B. Console.WriteLine("Enter a number:");
var num = Console.ReadLine();
Console.WriteLine(num * 2);

C. Console.WriteLine("Enter a number:");
int num = int.Parse(Console.ReadLine());
Console.WriteLine(num * 2);

D. int num = Console.ReadLine();
Console.WriteLine(num * 2);

Solution

1. Step 1: Check input reading and parsing

   Console.WriteLine("Enter a number:"); int num = int.Parse(Console.ReadLine()); Console.WriteLine(num * 2); reads input as string, parses to int, then doubles it correctly.

2. Step 2: Verify top-level usage and output

   Console.WriteLine("Enter a number:"); int num = int.Parse(Console.ReadLine()); Console.WriteLine(num * 2); uses top-level statements correctly without class or Main method, and prints the doubled value.

3. Final Answer:

   Console.WriteLine("Enter a number:"); int num = int.Parse(Console.ReadLine()); Console.WriteLine(num * 2); -> Option C

4. Quick Check:

   Parse input to int before math [OK]

Hint: Parse input string to int before math [OK]

Common Mistakes:

• Not parsing input string to int
• Using class and Main when top-level allowed
• Assigning Console.ReadLine() directly to int