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.

Practice

1. What is the role of a parameter in a C# method?

easy

A. It acts as a placeholder for values passed to the method.

B. It stores the result returned by the method.

C. It defines the method's name.

D. It calls another method inside the current method.

Solution

1. Step 1: Understand method definition

   Parameters are declared in the method signature to receive values.

2. Step 2: Differentiate parameters from other parts

   Parameters are not method names or return values but placeholders for inputs.

3. Final Answer:

   It acts as a placeholder for values passed to the method. -> Option A

4. Quick Check:

   Parameter = placeholder [OK]

Hint: Parameters hold input spots in methods [OK]

Common Mistakes:

• Confusing parameters with return values
• Thinking parameters are method names
• Mixing parameters with method calls

2. Which of the following is the correct way to define a method with one integer parameter named number in C#?

easy

A. void PrintNumber(number int) { }

B. void PrintNumber(int) { }

C. void PrintNumber(int number) { }

D. void PrintNumber(number) { }

Solution

1. Step 1: Recall C# parameter syntax

   Parameters require type first, then name: int number.

2. Step 2: Check each option

   void PrintNumber(int number) { } matches correct syntax; others have wrong order or missing names.

3. Final Answer:

   void PrintNumber(int number) { } -> Option C

4. Quick Check:

   Type before name in parameters [OK]

Hint: Parameter syntax: type then name [OK]

Common Mistakes:

• Swapping parameter type and name
• Omitting parameter name
• Using parentheses without parameter types

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

void Greet(string name) {
    Console.WriteLine($"Hello, {name}!");
}

Greet("Alice");

medium

A. Hello, Alice!

B. Hello, name!

C. Hello, !

D. Error: Missing argument

Solution

1. Step 1: Identify the parameter and argument

   The method Greet has a parameter name and is called with argument "Alice".

2. Step 2: Understand string interpolation output

   The output will replace {name} with "Alice" in the printed string.

3. Final Answer:

   Hello, Alice! -> Option A

4. Quick Check:

   Argument replaces parameter in output [OK]

Hint: Arguments fill parameters when calling methods [OK]

Common Mistakes:

• Printing parameter name literally
• Forgetting to pass argument
• Confusing parameter with variable

4. What is wrong with this method call?

void PrintSum(int a, int b) {
    Console.WriteLine(a + b);
}

PrintSum(5);

medium

A. Too many arguments passed.

B. Too few arguments passed.

C. Parameter types do not match arguments.

D. Method name is incorrect.

Solution

1. Step 1: Check method parameters

   The method PrintSum requires two integer parameters: a and b.

2. Step 2: Check method call arguments

   The call PrintSum(5); provides only one argument instead of two.

3. Final Answer:

   Too few arguments passed. -> Option B

4. Quick Check:

   Parameter count must match argument count [OK]

Hint: Count arguments to match parameters [OK]

Common Mistakes:

• Passing fewer arguments than parameters
• Ignoring method signature requirements
• Assuming default values without specifying

5. You want to create a method CalculateArea that takes two parameters width and height and returns their product. Which method signature and call correctly use parameters and arguments?

hard

A. Method: int CalculateArea(int width, int height)Call: CalculateArea(5);

B. Method: int CalculateArea(width, height)Call: CalculateArea(5, 10);

C. Method: void CalculateArea(int width, int height)Call: CalculateArea(5, 10);

D. Method: int CalculateArea(int width, int height)Call: CalculateArea(5, 10);

Solution

1. Step 1: Check method signature correctness

   Method: int CalculateArea(int width, int height)
   Call: CalculateArea(5, 10); correctly declares parameter types and names and returns int.

2. Step 2: Check method call arguments

   Method: int CalculateArea(int width, int height)
   Call: CalculateArea(5, 10); calls method with two integer arguments matching parameters.

3. Step 3: Analyze other options

   Method: int CalculateArea(width, height)
   Call: CalculateArea(5, 10); misses types in parameters; Method: int CalculateArea(int width, int height)
   Call: CalculateArea(5); passes only one argument; Method: void CalculateArea(int width, int height)
   Call: CalculateArea(5, 10); returns void, so no product returned.

4. Final Answer:

   Method with int parameters and int return, called with two arguments. -> Option D

5. Quick Check:

   Signature and call must match parameters and arguments [OK]

Hint: Match parameter types and argument count exactly [OK]

Common Mistakes:

• Omitting parameter types
• Passing wrong number of arguments
• Using void return when value needed