Method declaration and calling in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a method named Greet that prints a message.

C Sharp (C#)

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

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

AGreet

BPrint

CSayHello

DMessage

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name different from the one asked.

Leaving the method name blank.

The method name should be Greet as specified.

2fill in blank

medium

Complete the code to call the method named Greet.

C Sharp (C#)

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

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

AMessage

BPrint

CGreet

DSayHello

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method with a wrong name.

Forgetting the parentheses when calling the method.

To call the method, use its exact name Greet followed by parentheses.

3fill in blank

hard

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

C Sharp (C#)

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

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

Avoid

Bint

Cstring

Dbool

Attempts:

3 left

💡 Hint

Common Mistakes

Using a return type other than void without returning a value.

Leaving the return type blank.

The method does not return a value, so the return type should be void.

4fill in blank

hard

Fill both blanks to declare a method named Add that returns the sum of two integers a and b.

C Sharp (C#)

static [1] Add(int a, int b) {
    return a [2] b;
}

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

Aint

B+

C-

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using void as return type when returning a value.

Using subtraction instead of addition.

The method returns an integer, so the return type is int. The sum uses the + operator.

5fill in blank

hard

Fill all three blanks to declare and call a method named Multiply that returns the product of two integers x and y.

C Sharp (C#)

static [1] Multiply(int x, int y) {
    return x [2] y;
}

static void Main() {
    int result = Multiply([3], 5);
    Console.WriteLine(result);
}

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

Aint

B*

C3

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong return type.

Using wrong operator.

Passing wrong argument value.

The method returns an integer, so int is the return type. The multiplication operator is *. The method is called with 3 and 5.

Practice

1. What is the correct way to declare a method named Greet that returns nothing and takes no parameters in C#?

easy

A. public Greet() void { }

B. void Greet[] { }

C. void Greet { }

D. public void Greet() { }

Solution

1. Step 1: Understand method declaration syntax

   A method declaration starts with an access modifier (like public), then the return type (void means no return), then the method name, and parentheses for parameters.

2. Step 2: Check each option's syntax

   public void Greet() { } correctly uses 'public void Greet() { }'. Options A, B, and D have syntax errors like wrong brackets or missing parentheses.

3. Final Answer:

   public void Greet() { } -> Option D

4. Quick Check:

   Method declaration = public void Greet() { } [OK]

Hint: Method syntax: access + return type + name + parentheses [OK]

Common Mistakes:

• Using square brackets [] instead of parentheses ()
• Omitting parentheses after method name
• Placing return type after method name

2. Which of the following is the correct way to call a method named CalculateSum that takes two integers as parameters?

easy

A. CalculateSum 5, 10;

B. CalculateSum[5, 10];

C. CalculateSum(5, 10);

D. CalculateSum{5, 10};

Solution

1. Step 1: Recall method call syntax

   To call a method, use its name followed by parentheses containing arguments separated by commas.

2. Step 2: Evaluate each option

   CalculateSum(5, 10); uses parentheses correctly. Options B, C, and D use incorrect brackets or omit parentheses, causing syntax errors.

3. Final Answer:

   CalculateSum(5, 10); -> Option C

4. Quick Check:

   Method call = name + parentheses + arguments [OK]

Hint: Call methods with parentheses and comma-separated arguments [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Omitting parentheses when calling methods
• Using curly braces for method calls

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

public class Program {
  public static int Double(int x) {
    return x * 2;
  }
  public static void Main() {
    int result = Double(4);
    Console.WriteLine(result);
  }
}

medium

A. 8

B. 4

C. 16

D. Compilation error

Solution

1. Step 1: Understand the method Double

   The method takes an integer x and returns x multiplied by 2.

2. Step 2: Trace the method call in Main

   Double(4) returns 4 * 2 = 8, which is stored in result and printed.

3. Final Answer:

   8 -> Option A

4. Quick Check:

   Double(4) = 8 [OK]

Hint: Multiply input by 2, then print result [OK]

Common Mistakes:

• Confusing return value with input
• Expecting 16 by squaring instead of doubling
• Thinking method does not return a value

4. Identify the error in the following method declaration and fix it:

public int AddNumbers(int a, int b) {
  int sum = a + b;
}

medium

A. Add a return statement: return sum;

B. Change method return type to void

C. Remove parameters from method

D. Add semicolon after method name

Solution

1. Step 1: Check method return type and body

   The method declares it returns an int but does not return any value.

2. Step 2: Fix by adding a return statement

   Adding return sum; returns the calculated value, matching the return type.

3. Final Answer:

   Add a return statement: return sum; -> Option A

4. Quick Check:

   Return value needed for non-void methods [OK]

Hint: Non-void methods must return a value [OK]

Common Mistakes:

• Forgetting to return a value in non-void methods
• Changing return type incorrectly
• Removing parameters unnecessarily

5. You want to create a method IsEven that returns true if a number is even, otherwise false. Which of the following is the correct method declaration and call to check if 7 is even?

hard

A. public bool IsEven(int num) { if(num / 2 == 0) return true; else return false; } ... bool result = IsEven(7);

B. public bool IsEven(int num) { return num % 2 == 0; } ... bool result = IsEven(7);

C. public void IsEven(int num) { if(num % 2 == 0) return true; else return false; } ... bool result = IsEven(7);

D. public int IsEven(int num) { return num % 2; } ... int result = IsEven(7);

Solution

1. Step 1: Check method return type and logic

   Method should return bool and use modulo (%) to check evenness. public bool IsEven(int num) { return num % 2 == 0; } ... bool result = IsEven(7); correctly returns true if remainder is 0.

2. Step 2: Verify method call and variable type

   public bool IsEven(int num) { return num % 2 == 0; } ... bool result = IsEven(7); calls IsEven(7) and stores result in a bool variable, matching the method return type.

3. Final Answer:

   public bool IsEven(int num) { return num % 2 == 0; } ... bool result = IsEven(7); -> Option B

4. Quick Check:

   Use modulo and bool return for even check [OK]

Hint: Use 'return num % 2 == 0;' for even check [OK]

Common Mistakes:

• Using division instead of modulo for even check
• Returning int instead of bool
• Declaring method void but trying to return a value