Introduction(Understand the basic structure of a c# program)

Hello Everyone!! In this series of tutorial we are going to discuss about the basic elements of C#. Like all others OOP (Object Oriented Programming) languages C# is also an OOP language that means the three qualities that make a programming language object oriented can be found in C# also. The qualities are-

  • Encapsulation
  • Polymorphism
  • Inheritance

We will understand each of this qualities in the later session of this series. In this article we will understand the basic structure of a C# program. All the sample programs of this series is going to be a Console Application and we are using Visual Studio as the IDE. So first we will learn how to open a console application in Visual Studio.

A console application is nothing but a program that can be executed in the command prompt of our Computer. To open a console application first we have to open visual studio then from the menu choose File-> New-> Project. Then another windows will pop up then in the popup window choose Visual C# in the left and you can see console application there. Choose Console Application template and give it a suitable name, you can choose the location where to save this program in your pc from here also. When you choose everything click the OK button to create the program.

OpenNewProject

When you click the OK button the program will be created and you will see the following code –

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace introduction
{
    class Program
    {
        static void Main()
        {
        }
    }
}

Now for simplicity we will remove some code from the above and make it a very basic structure of a C# program. After removing those code the above program will looks like the following-

using System;

class Program
{
    static void Main()
    {

    }
}

The above program can be said as a very basic structure of C# program. Now we will describe each line of the above program.
The first line is-
using System;

This is called the namespace declaration. A namespace is nothing but a collection of some classes, enums, structs, interfaces and delegates. What are all these we will discuss later. A namespace can hold another namespace also. For now to understand the above line we can say there are some built-in methods in this namespace called System and to use those methods and classes we have to declare the namespace by using keyword at the top. Just for an example if we want to print something in the console then we can write the following code-

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello world");
    }
}

To run the above code press Ctrl+F5. Then the command prompt should appear with the message “Hello world”.
The definition of this Writeline method is written in the namespace called System. Now if we remove the using System; line from our code then we will get an error in the line Console.WriteLine(“Hello world”);
Because now the definition of WRITELINE method is missing from our program. If we want to remove the namespace declaration then we have to write the name in the line when we use a method belongs to that namespace as follows-

class Program
{
    static void Main()
    {
        System.Console.WriteLine("Hello world");
    }
}

Namespace is used to organize our code more effectively. If you don’t use the namespace declaration at the top then each time when you use a method you have to write its namespace which is more time consuming. So the use of namespace declaration is important.
Now the next thing in our basic structure is a Class declaration. We assume that you are familiar with OOP and if you are so then you are already known to class. Like other OOP language the class declaration in C# is exactly same. Anything you write in C# is belongs to a class. There are different types of class in C#. We will discuss it later in this series. Just for now we can say any piece of code should be inside of a class. Here the name of our class is Program.
Then there is also a method named Main and it is a static method. What is static method and class we will discuss it later. Now what we have to understand is the Main method is the starting point of our program. When we run our code it start to execute each line from the beginning of Main method and end when the Main method ends. To prove this, we can declare another same method named Main2 and in this method we print another message to differentiate the two method. We can consider the following piece of code-

using System;
class Program
{
    static void Main2()
    {
        Console.WriteLine("Another Message");
    }
    static void Main()
    {
        Console.WriteLine("Hello world");
    }
}

Here if we run the program we will see that only the message “Hello world” is printed. Another method named MAIN2 is not executed. So it’s proved that our program start from Main method and terminate when the MAIN method terminates. If we want to print the 2nd message then we have to call the MAIN2 method from MAIN method before it terminates. We can do it by the following-

using System;
class Program
{
    static void Main2()
    {
        Console.WriteLine("Another Message");
    }
    static void Main()
    {
        Console.WriteLine("Hello world");
        Main2();
    }
}

Now we should be able to see both messages.
In this article we see the basic structure of a C# programming and we can sum up with the following decisions from the above discussion-
• The namespace declaration using System; indicates that you are using System namespace
• A namespace is a collection of Classes, Structs, Delegates, Enums, Interfaces and used to organize the code more effectively.
• Our program starts with the Main method and terminates when the Main method terminates.

 

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