Optional parameters in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of method with optional parameters

What is the output of this C# code when calling Greet() without arguments?

C Sharp (C#)

using System;
class Program {
    static void Greet(string name = "Guest", int times = 1) {
        for (int i = 0; i < times; i++) {
            Console.WriteLine($"Hello, {name}!");
        }
    }
    static void Main() {
        Greet();
    }
}

A Hello, Guest!

B Hello, !

C Hello, Guest!\nHello, Guest!

D Compilation error

💡 Hint

Check the default values of the parameters in the method signature.

The method Greet has two optional parameters: name with default "Guest" and times with default 1. Calling Greet() uses these defaults, so it prints "Hello, Guest!" once.

❓ Predict Output

intermediate

Output with named and optional parameters

What is the output of this code snippet?

C Sharp (C#)

using System;
class Program {
    static void Display(string message = "Hi", int count = 2) {
        for (int i = 0; i < count; i++) {
            Console.WriteLine(message);
        }
    }
    static void Main() {
        Display(count: 3);
    }
}

A 3\n3\n3

B Hi\nHi

C Hi\nHi\nHi

D Compilation error

💡 Hint

Named parameters can be used to specify only some arguments.

The call Display(count: 3) uses the default message "Hi" and overrides count to 3, so it prints "Hi" three times.

🔧 Debug

advanced

Identify the error with optional parameters

What error does this code produce when compiled?

C Sharp (C#)

class Program {
    static void Print(int x = 5, int y) {
        System.Console.WriteLine(x + y);
    }
    static void Main() {
        Print(3);
    }
}

A CS1501: No overload for method 'Print' takes 1 arguments

B No error, outputs 8

C CS0120: An object reference is required for the non-static field

D CS1737: Optional parameters must appear after all required parameters

💡 Hint

Check the order of optional and required parameters in method signature.

In C#, optional parameters must come after all required parameters. Here, x is optional but y is required and comes after x, causing CS1737.

❓ Predict Output

advanced

Output with multiple optional parameters and named arguments

What is the output of this program?

C Sharp (C#)

using System;
class Program {
    static void Info(string name = "Unknown", int age = 0, string city = "Nowhere") {
        Console.WriteLine($"Name: {name}, Age: {age}, City: {city}");
    }
    static void Main() {
        Info(city: "Paris", name: "Alice");
    }
}

A Name: Alice, Age: 0, City: Paris

B Name: Unknown, Age: 0, City: Paris

C Name: Alice, Age: 0, City: Nowhere

D Compilation error due to argument order

💡 Hint

Named arguments can be passed in any order.

The call uses named arguments city and name, so age uses default 0. Output shows name Alice, age 0, city Paris.

🧠 Conceptual

expert

Behavior of optional parameters with method overloading

Given these two methods, what happens when Test(5) is called?

C Sharp (C#)

class Program {
    static void Test(int x, int y = 10) {
        System.Console.WriteLine($"Method1: x={x}, y={y}");
    }
    static void Test(int x) {
        System.Console.WriteLine($"Method2: x={x}");
    }
    static void Main() {
        Test(5);
    }
}

A Method1: x=5, y=10

B Method2: x=5

C Compilation error due to ambiguous call

D Runtime error

💡 Hint

Consider how C# resolves overloaded methods with optional parameters.

C# prefers the method with exact parameter match over one with optional parameters. So Test(int x) is called, printing Method2.