Basic Structure of a C# Program

1. Namespace Declaration

   • Namespaces are used to organize code and prevent naming conflicts.

2. Class Declaration

   • All C# programs are built around classes. A class is a blueprint for creating objects.

3. Main Method

   • The entry point of a C# application. The execution of the program starts from the Main method.

4. Methods

   • Functions defined within a class that perform specific tasks.

5. Variables

   • Used to store data. Variables must be declared with a specific type.

Example of a C# Program

Here’s a simple example of a C# program that demonstrates the above structure. This program takes user input, processes it, and displays a message.

csharp
1using System;  // Importing the System namespace
2
3namespace HelloWorldApp  // Declaring a namespace
4{
5    class Program  // Declaring a class named Program
6    {
7        // The Main method - the entry point of the program
8        static void Main(string[] args)
9        {
10            // Declare a variable to store user input
11            string userName;
12
13            // Prompt the user for input
14            Console.Write("Enter your name: ");
15            
16            // Read user input from the console
17            userName = Console.ReadLine();
18
19            // Call a method to display a greeting
20            GreetUser (userName);
21        }
22
23        // A method to greet the user
24        static void GreetUser (string name)
25        {
26            // Display a greeting message
27            Console.WriteLine($"Hello, {name}! Welcome to the C# program.");
28        }
29    }
30}

Explanation of Each Part

1. Using Directive

   csharp
   1using System;

   • This line imports the System namespace, which contains fundamental classes and base classes that define commonly-used types, such as Console.

2. Namespace Declaration

   csharp
   1namespace HelloWorldApp

   • This declares a namespace called HelloWorldApp. Namespaces help organize code and prevent naming conflicts between classes.

3. Class Declaration

   csharp
   1class Program

   • This defines a class named Program. In C#, all executable code must reside within a class or struct.

4. Main Method

   csharp
   1static void Main(string[] args)

   • The Main method is the entry point of the program. It is marked as static, meaning it can be called without creating an instance of the class.
   • The string[] args parameter is an array of strings that can hold command-line arguments (not used in this example).

5. Variable Declaration

   csharp
   1string userName;

   • This line declares a variable userName of type string to store the user's name.

6. Input and Output

   csharp
   1Console.Write("Enter your name: ");
   2userName = Console.ReadLine();

   • Console.Write displays a prompt for the user to enter their name.
   • Console.ReadLine() reads the input from the console and stores it in the userName variable.

7. Method Call

   csharp
   1GreetUser (userName);

   • This line calls the GreetUser  method, passing userName as an argument.

8. Method Definition

   csharp
   1static void GreetUser (string name)
   2{
   3    Console.WriteLine($"Hello, {name}! Welcome to the C# program.");
   4}

   • This defines a method called GreetUser  that takes a string parameter name.
   • It uses string interpolation (the $ symbol) to create a greeting message that includes the user's name and displays it using Console.WriteLine().