What is C# - Practice Questions & Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the primary use of C#?

C# is a programming language. What is it mainly used for?

A Building Windows desktop applications and web services

B Creating databases and managing data with SQL

C Designing website layouts with HTML and CSS

D Writing scripts for Linux shell commands

💡 Hint

Think about what kind of programs you can build with C# on Windows.

C# is mainly used to build Windows desktop apps, web services, and games using frameworks like .NET.

❓ Predict Output

intermediate

What is the output of this C# code?

Look at this C# program. What will it print?

C Sharp (C#)

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

A 5 + 3

B 53

C Error: Cannot add integers

D 8

💡 Hint

Adding two numbers returns their sum.

The program adds 5 and 3, printing 8.

🔧 Debug

advanced

What error does this C# code produce?

What error will this code cause when run?

C Sharp (C#)

using System;
class Program {
  static void Main() {
    int number = "10";
    Console.WriteLine(number);
  }
}

A Output: 10

B Runtime error: NullReferenceException

C Compile-time error: Cannot convert string to int

D Compile-time error: Missing semicolon

💡 Hint

Check the type assigned to an integer variable.

You cannot assign a string value to an int variable in C# without conversion.

📝 Syntax

advanced

Which option correctly declares a method in C#?

Choose the correct way to declare a method that returns an integer and takes no parameters.

A int GetNumber() { return 5; }

B GetNumber() int { return 5; }

C int GetNumber { return 5; }

D int GetNumber() => { 5; }

💡 Hint

Remember the order: return type, method name, parentheses, braces.

Option A follows correct C# syntax for method declaration.

🚀 Application

expert

What is the value of 'result' after running this C# code?

Consider this code snippet. What is the value of result after execution?

C Sharp (C#)

using System;
class Program {
  static int Multiply(int a, int b = 2) {
    return a * b;
  }
  static void Main() {
    int result = Multiply(3);
    Console.WriteLine(result);
  }
}

A 3

B 6

C 5

D Error: Missing argument for parameter 'b'

💡 Hint

Check the default value of parameter b.

The method Multiply uses default value 2 for b, so 3 * 2 = 6.