Why methods are needed in C Sharp (C#) - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a method that prints a greeting.

C Sharp (C#)

public void [1]() {
    Console.WriteLine("Hello, friend!");
}

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

APrint

BMain

CGreet

DStart

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Main' as method name here causes confusion with program entry point.

Choosing unrelated names like 'Start' or 'Print' does not match the greeting.

The method name should be Greet to match the greeting action.

2fill in blank

medium

Complete the code to call the method that prints a greeting.

C Sharp (C#)

class Program {
    static void Main() {
        [1]();
    }

    static void Greet() {
        Console.WriteLine("Hello, friend!");
    }
}

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

APrint

BGreet

CStart

DMain

Attempts:

3 left

💡 Hint

Common Mistakes

Calling 'Main' inside Main causes recursion error.

Using 'Print' or 'Start' which are not defined methods.

You call the method by its name Greet to print the greeting.

3fill in blank

hard

Fix the error in the method definition by completing the missing return type.

C Sharp (C#)

public [1] Greet() {
    Console.WriteLine("Hello!");
}

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

Avoid

Bbool

Cstring

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'int' or 'string' without returning a value causes errors.

Forgetting to specify 'void' when no return is needed.

The method does not return a value, so its return type must be void.

4fill in blank

hard

Fill both blanks to define and call a method that adds two numbers and returns the result.

C Sharp (C#)

public static int Add(int a, int b) {
    return a [1] b;
}

static void Main() {
    int sum = Add(3, 4);
    Console.WriteLine(sum [2] 0);
}

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

A+

B>

C<

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' instead of '+' in addition.

Using '<' instead of '>' in comparison.

The method adds two numbers using '+'. The Console.WriteLine checks if sum is greater than 0 using '>'.

5fill in blank

hard

Fill all three blanks to define a method that checks if a number is even and call it in Main.

C Sharp (C#)

public static bool IsEven(int num) {
    return num [1] 2 [2] 0;
}

static void Main() {
    bool result = IsEven([3]);
    Console.WriteLine(result);
}

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

A%

B==

C4

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '==' causes wrong result.

Passing wrong number to IsEven.

The method uses '%' to get remainder, '==' to check equality with 0, and calls IsEven with 4.

Practice

1. Why do programmers use methods in C# programs?

easy

A. To organize code into small, clear parts for better understanding

B. To make the program run faster by skipping code

C. To write code only once and never use it again

D. To make the program use more memory

Solution

1. Step 1: Understand the purpose of methods

   Methods help break down code into smaller, manageable pieces.

2. Step 2: Identify the correct reason

   Organizing code into small parts makes it easier to read and maintain.

3. Final Answer:

   To organize code into small, clear parts for better understanding -> Option A

4. Quick Check:

   Methods organize code = A [OK]

Hint: Methods break code into parts for clarity [OK]

Common Mistakes:

• Thinking methods speed up the program directly
• Believing methods increase memory use
• Assuming methods are for one-time code only

2. Which of the following is the correct way to define a method named Greet that returns nothing and takes no parameters in C#?

easy

A. def Greet() { Console.WriteLine("Hello"); }

B. void Greet() { Console.WriteLine("Hello"); }

C. function Greet() { Console.WriteLine("Hello"); }

D. Greet() => Console.WriteLine("Hello");

Solution

1. Step 1: Recall C# method syntax

   In C#, methods use the return type, name, parentheses, and braces.

2. Step 2: Match syntax with options

   void Greet() { Console.WriteLine("Hello"); } uses void return type and correct braces, matching C# syntax.

3. Final Answer:

   void Greet() { Console.WriteLine("Hello"); } -> Option B

4. Quick Check:

   C# method syntax = C [OK]

Hint: C# methods start with return type and name [OK]

Common Mistakes:

• Using 'function' keyword (JavaScript style)
• Using 'def' keyword (Python style)
• Using arrow syntax without proper context

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

void PrintMessage() {
    Console.WriteLine("Hello World");
}

PrintMessage();

medium

A. Syntax error

B. PrintMessage

C. No output

D. Hello World

Solution

1. Step 1: Understand method definition and call

   The method PrintMessage prints "Hello World" when called.

2. Step 2: Check the method call

   The method is called correctly with PrintMessage();, so it runs and prints the message.

3. Final Answer:

   Hello World -> Option D

4. Quick Check:

   Method call prints message = D [OK]

Hint: Method call runs code inside method [OK]

Common Mistakes:

• Thinking method name prints instead of output
• Assuming no output without return
• Confusing syntax error with correct code

4. Identify the error in this C# method and how to fix it:

void ShowNumber()
{
    Console.WriteLine(number);
}

int number = 5;
ShowNumber();

medium

A. The variable 'number' is used before declaration; move declaration above method

B. Method must return int instead of void

C. Missing semicolon after method call

D. Method name should be lowercase

Solution

1. Step 1: Check variable scope

   The variable 'number' is declared after the method, so it's not visible inside the method.

2. Step 2: Fix variable scope

   Move the declaration of 'number' before the method or pass it as a parameter.

3. Final Answer:

   The variable 'number' is used before declaration; move declaration above method -> Option A

4. Quick Check:

   Variable scope error = B [OK]

Hint: Variables must be declared before use in methods [OK]

Common Mistakes:

• Thinking method return type causes error
• Missing semicolon is not the issue here
• Ignoring case sensitivity of method names

5. You want to reuse code that calculates the area of a rectangle multiple times with different sizes. How should you use methods in C# to do this efficiently?

hard

A. Write a method that prints the area directly without parameters

B. Copy and paste the area calculation code everywhere you need it

C. Write a method that takes width and height as parameters and returns the area

D. Use a global variable to store area and update it each time

Solution

1. Step 1: Identify the need for reusable code

   Calculating area multiple times means code should be reusable with different inputs.

2. Step 2: Use method with parameters and return value

   A method that takes width and height and returns area allows reuse without copying code.

3. Final Answer:

   Write a method that takes width and height as parameters and returns the area -> Option C

4. Quick Check:

   Reusable method with parameters = A [OK]

Hint: Use parameters and return to reuse code easily [OK]

Common Mistakes:

• Copy-pasting code instead of using methods
• Printing inside method limits reuse
• Using global variables causes confusion