Method declaration and calling in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a method call with parameters

What is the output of the following C# program?

C Sharp (C#)

using System;
class Program {
    static int Multiply(int a, int b) {
        return a * b;
    }
    static void Main() {
        Console.WriteLine(Multiply(3, 4));
    }
}

A Error: Method Multiply not found

B 7

C 12

D 34

💡 Hint

Look at what the Multiply method returns when given 3 and 4.

The Multiply method returns the product of a and b. 3 * 4 = 12, so the output is 12.

❓ Predict Output

intermediate

Return value from a void method

What will happen when this C# code runs?

C Sharp (C#)

using System;
class Program {
    static void PrintMessage() {
        Console.WriteLine("Hello World");
    }
    static void Main() {
        var result = PrintMessage();
        Console.WriteLine(result == null);
    }
}

A Hello World\nTrue

B Compilation error: Cannot assign void to variable

C Hello World\nFalse

D Runtime error

💡 Hint

Void methods do not return a value and cannot be assigned to a variable.

In C#, you cannot assign the result of a void method to a variable because void methods do not return a value. This causes a compilation error.

❓ Predict Output

advanced

Method overloading and output

What is the output of this C# program?

C Sharp (C#)

using System;
class Program {
    static void Display(int x) {
        Console.WriteLine("Int: " + x);
    }
    static void Display(string x) {
        Console.WriteLine("String: " + x);
    }
    static void Main() {
        Display(5);
        Display("5");
    }
}

A String: 5\nInt: 5

B Runtime error

C Compilation error: Ambiguous call to Display

D Int: 5\nString: 5

💡 Hint

Look at how method overloading works with different parameter types.

The method Display is overloaded for int and string. Calling Display(5) calls the int version, Display("5") calls the string version.

❓ Predict Output

advanced

Output of recursive method call

What will this C# program print?

C Sharp (C#)

using System;
class Program {
    static int Factorial(int n) {
        if (n <= 1) return 1;
        return n * Factorial(n - 1);
    }
    static void Main() {
        Console.WriteLine(Factorial(4));
    }
}

A 24

B 10

C Error: Stack overflow

D 1

💡 Hint

Factorial of 4 is 4 * 3 * 2 * 1.

The Factorial method calls itself recursively until n is 1 or less, multiplying all numbers down to 1. 4! = 24.

❓ Predict Output

expert

Effect of method parameters on output

Consider this C# code. What is the output after running Main?

C Sharp (C#)

using System;
class Program {
    static void ChangeValue(int x) {
        x = 10;
    }
    static void Main() {
        int a = 5;
        ChangeValue(a);
        Console.WriteLine(a);
    }
}

A 5

B 10

C Compilation error

D Runtime error

💡 Hint

Think about whether the method changes the original variable or just a copy.

In C#, method parameters are passed by value by default. ChangeValue changes only the copy of a, so a remains 5.