Basic Structure Of A C# Program Complete Guide

Top 10 Questions and Answers on the Basic Structure of a C# Program

1. What is the mandatory part of every C# program?

Answer: Every C# program must have a Main method, which serves as the entry point of the application. The Main method can be defined in one of two ways:

• static void Main(string[] args)
• static int Main(string[] args)

The first form is the most common, where the program runs and does not return any value. The second form returns an integer, typically used for error codes in console applications.

2. How do you define a namespace in C#?

Answer: A namespace in C# is used to organize code into logical groups, preventing name conflicts. Namespaces are defined using the namespace keyword:

namespace MyNamespace
{
    class MyProgram
    {
        static void Main(string[] args)
        {
            // Code goes here
        }
    }
}

3. What is the use of using directives in a C# program?

Answer: using directives are used to include namespaces, allowing you to reference types in those namespaces without needing to include their full namespace path. For example:

using System;

class MyProgram
{
    static void Main(string[] args)
    {
        Console.WriteLine("Hello, World!");
    }
}

Here, using System; lets you use Console.WriteLine without writing System.Console.WriteLine.

4. How do you create a class in C#?

Answer: A class in C# is defined using the class keyword. It can contain methods, properties, fields, and other members:

class MyClass
{
    public void MyMethod()
    {
        // Method code
    }
}

5. What are access modifiers in C# and why are they important?

Answer: Access modifiers determine the visibility and accessibility of classes, methods, and other members. The primary access modifiers are:

• public: Accessible from anywhere.
• private: Accessible only within the containing class.
• protected: Accessible within the class and by derived classes.
• internal: Accessible only within files in the same assembly.
• protected internal: Accessible within the class and by derived classes, even if they are in a different assembly.

Access modifiers ensure encapsulation, a key principle of object-oriented programming.

6. What is the difference between static and instance members in C#?

Answer: In C#, members can be static or instance.

• Static members belong to the type itself rather than any particular object of the type. They can be accessed directly using the class name without creating an object. For example:

class MyClass
{
    public static void MyStaticMethod()
    {
        // Code goes here
    }
}
// Using the static method
MyClass.MyStaticMethod();

• Instance members belong to an instance of a class. You need to create an object to access an instance member. For example:

class MyClass
{
    public void MyInstanceMethod()
    {
        // Code goes here
    }
}
// Using the instance method
MyClass obj = new MyClass();
obj.MyInstanceMethod();

7. How do you pass arguments to the Main method in C#?

Answer: The Main method can optionally accept a string[] parameter that represents command-line arguments:

class MyProgram
{
    static void Main(string[] args)
    {
        if (args.Length > 0)
        {
            Console.WriteLine("First argument: " + args[0]);
        }
        else
        {
            Console.WriteLine("No arguments provided.");
        }
    }
}

When you run this program from the command line with arguments, such as MyProgram.exe arg1 arg2, the args array will contain those arguments.

8. What is the purpose of the Console.WriteLine method in C#?

Answer: Console.WriteLine is a method of the System namespace’s Console class, used to output text and a newline to the console:

Console.WriteLine("Hello, World!");
// Outputs: Hello, World!
// Followed by a newline character

It’s useful for displaying information to the user or for debugging purposes.

9. What is a comment in C# and how do you write it?

Answer: Comments in C# are used to explain or annotate code. They are ignored by the compiler and do not affect the program’s execution. C# supports three types of comments:

• Single-line comments: Use //

// This is a single-line comment

• Multi-line comments: Use /* */

/*
  This is a
  multi-line comment
*/

• XML documentation comments: Use /// (commonly used for generating documentation)

/// <summary>
/// This method prints a message.
/// </summary>

10. How do you create an object of a class in C#?

Answer: To create an object of a class, you use the new keyword followed by the class name and parentheses. This allocates memory for the object and calls the class constructor:

class MyClass
{
    public void MyMethod()
    {
        Console.WriteLine("Method called.");
    }
}

class MyProgram
{
    static void Main(string[] args)
    {
        MyClass myObject = new MyClass(); // Creating an object of MyClass
        myObject.MyMethod();              // Calling a method on the object
    }
}

Here, myObject is an instance of MyClass.