Introduction to CSharp

Introduction to C#

Difference between C# & .NET

• C# is a programming language.
• .NET is a framework for building applications on Windows.

• .NET framework consists of:

  1. Common Language Runtime(CLR)
     • CLR is used to convert the Intermediate Language (IL) code into the Native code which can be executed on the underlying hardware.
     • The process of converting IL code to Native code is called Just in Time(JIT) compilation.
  2. Class Library
     • A class library file is a collection of classes and namespaces in C# without any entry point method like ‘Main’.
     • Once we create a class library file it can be used in the C# project and classes inside it can be used as required.

Architecture of .NET Applications:

• Application consists of building blocks called classes.
• Class contains data/fields and methods.
  • Class: Car
  • Data: Make, Model, Color
  • Methods: Start (), Move ()
• Namespace is a container for related classes to organize large number of classes in a application.
• Assembly is a container of related namespaces and can be an exe or dll file.
• While compiling an application, the complier build one or more assemblies depending upon the code partition.

C# Program Structure:

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

namespace MyFirstCSharpProgram
{
	class Program
	{
		static void Main(string[] args)
		{
			// My first comment in C#
			Console.WriteLine("Hello World...");
		}
	}
}

Line No.s	Description
Lines 1-4	The using keyword is used to include the System and other namespaces in the programs.
Line 6	This is a namespace declaration. A namespace is collection of classes. Ex. The MyFirstCSharpProgram namespace contains the class Program.
Line 8	This is the class declaration, the class Program contains the data and method definitions that your program uses. Classes generally would contain more than one methods. Methods define the behaviour of the class. However, the Program class has only one method Main.
Line 10	It defines the Main method, which is the entry point for all C# programs. The Main method states what the class will do when executed.

Data Types in C#

• A data type specifies the size and type of variable values.
• There are two types of data type in C#:

Type	Description	Example
Primitive	Primitive data types are the main built-in types.	byte short int float double long char bool datetime string object
Non-Primitive	Non-Primitive data types are user defined data types.	class struct enum interface delegate array