Parameters and arguments in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method with default and named arguments

What is the output of this C# code when calling PrintMessage("Hello")?

C Sharp (C#)

using System;
class Program {
    static void PrintMessage(string message, int times = 2) {
        for (int i = 0; i < times; i++) {
            Console.WriteLine(message);
        }
    }
    static void Main() {
        PrintMessage("Hello");
    }
}

A Hello\nHello

B Hello

C Hello\nHello\nHello

D Compilation error

💡 Hint

Check the default value of the parameter times.

The method PrintMessage prints the message the number of times specified by times. Since times defaults to 2, it prints "Hello" twice.

🧠 Conceptual

intermediate

Understanding ref and out parameters

Which statement about ref and out parameters in C# is true?

A <code>out</code> parameters must be initialized before passing; <code>ref</code> parameters do not need to be initialized.

B <code>ref</code> parameters cannot be modified inside the method.

C Both <code>ref</code> and <code>out</code> parameters must be initialized before passing.

D <code>ref</code> parameters must be initialized before passing; <code>out</code> parameters do not need to be initialized before passing but must be assigned inside the method.

💡 Hint

Think about whether the variable needs a value before calling the method.

ref parameters require the variable to be initialized before passing. out parameters do not require initialization before passing but must be assigned a value inside the method before returning.

🔧 Debug

advanced

Identify the error with params keyword

What error will this code produce?

C Sharp (C#)

using System;
class Program {
    static void Sum(params int[] numbers) {
        int total = 0;
        foreach (int n in numbers) {
            total += n;
        }
        Console.WriteLine(total);
    }
    static void Main() {
        Sum(1, 2, 3);
        Sum(new int[] {4, 5, 6});
        Sum();
        Sum(7);
    }
}

A No error; outputs 6, 15, 0, 7

B Compilation error: params must be last parameter

C Runtime error: NullReferenceException

D Compilation error: params cannot be used with arrays

💡 Hint

Check how the params keyword works with arrays and multiple arguments.

The params keyword allows passing zero or more arguments or an array. All calls are valid and print the sum correctly.

❓ Predict Output

advanced

Output of method with ref parameter

What is the output of this code?

C Sharp (C#)

using System;
class Program {
    static void Increment(ref int number) {
        number += 5;
    }
    static void Main() {
        int x = 10;
        Increment(ref x);
        Console.WriteLine(x);
    }
}

A Compilation error: missing ref keyword

B 10

C 15

D Runtime error

💡 Hint

Remember that ref passes the variable by reference, so changes affect the original.

The method adds 5 to the original variable x because it is passed by reference.

❓ Predict Output

expert

Output of method with params and named arguments

What is the output of this code?

C Sharp (C#)

using System;
class Program {
    static void Display(string title, params int[] values) {
        Console.WriteLine(title);
        foreach (int v in values) {
            Console.Write(v + " ");
        }
        Console.WriteLine();
    }
    static void Main() {
        Display(title: "Numbers:", values: 1, 2, 3);
    }
}

A Runtime error

B Compilation error: named arguments must come after positional arguments

C Numbers:\n2 3

D Numbers:\n1 2 3

💡 Hint

Check the order of named and positional arguments in method calls.

In C#, named arguments must come after all positional arguments. Here, values is named but followed by positional arguments, causing a compilation error.