Return values and void methods in C Sharp (C#) - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make the method return an integer value.

C Sharp (C#)

public int GetNumber() {
    return [1];
}

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

Anull

B5

Ctrue

D"5"

Attempts:

3 left

💡 Hint

Common Mistakes

Returning a string instead of an integer.

Returning a boolean value.

Returning null in a method that expects int.

The method returns an integer, so returning 5 is correct.

2fill in blank

medium

Complete the code to call the method and store its return value.

C Sharp (C#)

int result = [1]();

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

AGetNumber

BPrintNumber

CShowMessage

DDisplay

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a void method that does not return a value.

Using a method name that does not exist.

The method GetNumber returns an int, so calling it and storing the result is correct.

3fill in blank

hard

Fix the error in the method so it compiles correctly.

C Sharp (C#)

public void PrintMessage() {
    [1] "Hello!";
}

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

Areturn

Bint

CConsole.WriteLine

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using return in a void method without a value.

Declaring a type inside the method body.

The method should print the message using Console.WriteLine. Using return here is incorrect because the method is void.

4fill in blank

hard

Complete the code to create a method that returns the sum of two integers.

C Sharp (C#)

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

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

A+

B-

C;

D,

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction instead of addition.

Forgetting the semicolon at the end of the return statement.

The method returns the sum of a and b. The operator is + and the statement ends with a semicolon ;.

5fill in blank

hard

Fill both blanks to create a method that returns the uppercase version of a string.

C Sharp (C#)

public string ToUpperCase(string input) {
    string result = input[1]();
    return [2];
    // End of method
}

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

A.ToUpper

Bresult

Dinput

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the parentheses after ToUpper.

Returning the wrong variable.

Adding extra code after return statement.

The method calls ToUpper() on the input string, stores it in result, then returns result. The last blank is empty because no extra code is needed after the return.

Practice

1. Which statement correctly describes a void method in C#?

easy

A. It does not return any value.

B. It must return an integer value.

C. It always returns a string.

D. It returns a boolean value.

Solution

1. Step 1: Understand the meaning of void in C#

   The keyword void means the method does not return any value.

2. Step 2: Compare with other return types

   Methods with other return types like int, string, or bool must return a value of that type, but void methods do not return anything.

3. Final Answer:

   It does not return any value. -> Option A

4. Quick Check:

   Void means no return value [OK]

Hint: Void means no value comes back from the method [OK]

Common Mistakes:

• Thinking void methods return a default value
• Confusing void with returning null
• Assuming void methods must return something

2. Which of the following is the correct syntax for a method that returns an integer value in C#?

easy

A. public void GetNumber() { return 5; }

B. public void GetNumber() { Console.WriteLine(5); return 5; }

C. public int GetNumber() { Console.WriteLine(5); }

D. public int GetNumber() { return 5; }

Solution

1. Step 1: Identify method return type and return statement

   The method declares int return type, so it must return an integer value using return.

2. Step 2: Check each option for correct syntax

   public int GetNumber() { return 5; } correctly declares int and returns 5. public void GetNumber() { return 5; } is void but tries to return a value (invalid). public int GetNumber() { Console.WriteLine(5); } returns nothing despite int return type. public void GetNumber() { Console.WriteLine(5); return 5; } is void but tries to return a value (invalid).

3. Final Answer:

   public int GetNumber() { return 5; } -> Option D

4. Quick Check:

   Return type matches returned value [OK]

Hint: Return type must match the returned value type [OK]

Common Mistakes:

• Returning a value from a void method
• Not returning a value from a non-void method
• Using Console.WriteLine instead of return

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

public class Program {
  public static int Add(int a, int b) {
    return a + b;
  }
  public static void Main() {
    int result = Add(3, 4);
    Console.WriteLine(result);
  }
}

medium

A. 7

B. 34

C. 0

D. Compile error

Solution

1. Step 1: Understand the Add method

   The method Add takes two integers and returns their sum.

2. Step 2: Trace the Main method execution

   Main calls Add(3, 4), which returns 7. Then it prints 7 to the console.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add returns sum; printed result is sum [OK]

Common Mistakes:

• Concatenating numbers as strings
• Confusing return with print
• Expecting void method to return value

4. Identify the error in this C# method:

public int Multiply(int x, int y) {
  int product = x * y;
}

medium

A. Incorrect method name.

B. Variables cannot be declared inside methods.

C. Missing return statement for non-void method.

D. Method parameters must be strings.

Solution

1. Step 1: Check method return type and body

   The method declares int return type but does not return any value.

2. Step 2: Identify missing return statement

   Since the method is not void, it must have a return statement returning an integer value like return product;.

3. Final Answer:

   Missing return statement for non-void method. -> Option C

4. Quick Check:

   Non-void methods must return a value [OK]

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

Common Mistakes:

• Forgetting to return a value in non-void methods
• Thinking variable declaration is invalid inside methods
• Assuming parameters must be strings

5. You want to create a method that prints a greeting message but does not return any value. Which method signature and body is correct in C#?

hard

A. public string Greet() { Console.WriteLine("Hello!"); return "Hello!"; }

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

C. public void Greet() { return "Hello!"; }

D. public string Greet() { Console.WriteLine("Hello!"); }

Solution

1. Step 1: Understand method purpose and return type

   The method should print a message and not return any value, so it should be void.

2. Step 2: Check each option for correctness

   public void Greet() { Console.WriteLine("Hello!"); } correctly uses void and prints the message without returning anything. public string Greet() { Console.WriteLine("Hello!"); return "Hello!"; } returns a string, which is not needed. public void Greet() { return "Hello!"; } tries to return a string in a void method (invalid). public string Greet() { Console.WriteLine("Hello!"); } declares string return type but does not return anything (invalid).

3. Final Answer:

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

4. Quick Check:

   Void method prints only, no return [OK]

Hint: Void methods do actions, no return needed [OK]

Common Mistakes:

• Returning a value from a void method
• Declaring return type but not returning
• Confusing printing with returning