1 C# Overview

About Microsoft. NET
All About Microsoft. NET

Microsoft. NET is one of the latest and new technologies introduced by Microsoft Corporation. Nowadays we use to connect to the internet using a computer and a remote computer responses via a web page and a collection of web pages are called as Web Sites. The Concept in .NET is that these websites can integrate with other sites and services using Standard Protocols like HTTP.

Microsoft .NET Platform comprises of  four core components such as:

• NET Building Block Services such as file storage, calendar called Passport. NET
• NET Device Software which will run on latest Internet Devices like Mobile Phones.
• NET user experience such as integrating this technology to user created documents (integrates with XML). For example if you code XML via a  .NET Language like C#, it will  automatically create XML document.
• NET infrastructure which includes  NET Framework (Common Language Runtime & .NET Framework Class Libraries) Microsoft Visual Studio.NET such as Visual Basic.NET ,Visual C++.NET etc  NET Enterprise Servers and Microsoft Windows. NET.

We can build robust, scalable, distributed applications with the help of .NET and the part that helps us to develop these applications is called the .NET Framework. The .NET Framework contains Common Language Runtime (CLR) and the .NET Framework class libraries also called as Base Class Libraries.

All the .NET languages (like C-sharp, VisualBasic.NET, Visual C++. NET etc) have the .NET Framework class libraries built into them. The .NET class Libraries also supports File I/O, database operations, XML (Extensible Markup Language) and SOAP (Simple Object Access Protocol). For example you can develop XML Pages by using C-sharp language.

When someone talks about .NET development, then you should understand that they are talking about .NET Framework. It includes a Runtime environment and a set of Class Libraries which is being used by a new language called C-sharp abbreviated as C# (more or less similar to  C/C++/Java family of languages) and all other .NET Languages. Simply speaking C-sharp is a new language for developing custom solutions for Microsoft's .NET Platform.

The runtime which we discussed just now  is also used by VisualStudio.NET. Visual Studio.NET Provides us with a visual environment to design and develop .NET Applications. Every language in VisualStudio.NET uses this runtime to execute its applications. Moreover these languages compiles its source code into an intermediate language upon compilation. Hence you can very well use a module written using C-sharp in a Visual Basic Application. For example you can design a user interface with Visual Basic.NET and write a DLL function using C-sharp.

Terms Associated with Microsoft .NET

Common Language Runtime 

Common Language Runtime also called CLR Provides a universal execution engine for developers code. It generates SOAP when it makes remote procedure calls. CLR is independent and is provided as part of the .NET Framework. The main features of CLR are as follows:

1. Managed Code 
2. Automatic application installation
3. Memory Management
4. Automatic Garbage Collection
5. Very high level of Security while executing

.NET Framework Class Libraries 

These class libraries works with any language under the common language runtime environment. It includes Visual Studio.NET, C-Sharp. Therefore if you are familiar with  one .NET language then you can easily migrate to other .NET Languages.

                 
Note:

1. All namespaces should have to be called in your Program by applying the keyword using. For example if your programs needs to call System namespace, then it should be applied in the program as using System.
2. Classes cannot be called along with the using directive.
3. The using directive applies only to namespaces, just like importing packages in Java. Hence the following code will result in compilation error, using System.Console. 

However you can create an alias like the following using mysys = System.Console. Then you have to apply the alias in your program as follows mysys.writeLine("Hello C#");

Common Language Specification (CLS) 

It is a set of rules that a language compiler must adhere to in order to create .NET Applications that run in the CLR. If you are going to create a compiler for .NET, you have to adhere to the rules enumerated in the common language specification and this enables us to create a club of CLS compliant languages.

Each such compiler will have the following features:

• Complete access to .NET Framework hierarchy
• High level of interoperability with other compliant languages like Visual Basic. NET etc.

For example a Visual Basic class can inherit from a C# Class.

You should note that the syntaxes and other programming structures differ from each of these languages. The only difference is that a developer well versed with a language such as C-sharp can easily program in Visual Basic.NET or Visual C++.NET without investing a lot or spending too long to learn a new language. 

Begin C-Sharp Programming
Getting Started with C-sharp

First of all let me welcome you to the world of this new programming language. I hope you will have a basic idea about Object Oriented Programming languages because many languages like Java, C++ have come by the past 5 years. However there will be no difficulty in learning this language if you are a fresher, because this tutorial and the coming ones will explain all the concepts and features right from the beginning.

Wherever required I explained the features involved in C-sharp by comparing them with Java. This will ensure smooth progress for experienced Programmers. I recommend you to install the appropriate software's outlined in the next section before learning this new language.

Basic Requirements needed to begin C-sharp Programming

1. .NET Framework Software Development Kit and
2. An Editor (like Notepad or DOS Editor) to write source codes.

Optional Requirements:

1. Visual C#. NET or
2. Visual C++ 6.0 included with VisualStudio 6.0

Installing .NET Framework SDK

As a first step you should install .NET SDK on your computer to begin C-sharp Programming. It can be downloaded from the Microsoft's Website. It is also available with almost all the popular computing magazine CD'S. It also comes with the complete documentation in the form of HTML Help.

At the time of this writing only beta version of the kit is available. This kit enables you to compile & execute the source code in C#, Visual Basic by using its built-in Command line Compiler (csc and vbc) and runtime Just In Time (JIT) Compiler. This is similar to Java Compiler (javac) and Java Interpreter (java) included 
with Java Development Kit.

You can also develop applications with C-sharp and Visual Basic by using Visual Studio.NET languages like Visual C#.NET and Visual Basic.NET. This will help you to develop windows based applications easily and with limited effort because you don't have to devote too much time in designing the user interface (Usage of WinForms). The only work left for you to do is to write the codings appropriately as per the .NET Standards.

About the Editors

Notepad is the best choice among developers using .NET SDK to develop C# applications. However it is not the most suitable editor since it does not support syntax coloring, code numberings etc. 

Developers can use Visual C++ 6.0 included with Visual Studio 6.0. However they should make some tweaking in the registry before using the same. It supports syntax colorings and other features such as finding line numbers (Ctrl+G). However it is dangerous for a new user to make changes in registry. Hence only advanced and experienced users can be able to use Visual Studio 6.0 for developing C#. It is not possible to compile and execute the applications from the Visual C++ 6.0 Environment. Hence there is not much use except some of the features listed above.

VisualStudio.NET provides all the integrated tools and wizards for creating C# and Visual Basic applications. It also supports features such as intellisense, Dynamic help. Moreover you can compile and execute your applications from the IDE itself.  Hence in order to experience the power of developing the .NET applications, you should try VisualStudio.NET.

Many Third Party editors are now available either from magazine's CD'S or can be downloaded from the internet. However it is up to you to decide upon which editor to use. I recommend you to try one common editor and learn the language in full.  

Your First Hello C# Program
Getting Started with Hello C-Sharp                 

After understanding the fundamentals of .NET and its Structure, let us now move on to look at a classic Hello C# Program. As I mentioned in the previous tutorial, you can use any text editor as per your Convenience.

Listing 3.1 gives the coding for this simple Hello C# Program.

using System ;
Class Hello 
{
Public static void Main ()
{Console.writeLine ("Hello C#"); 
} 
} //end of the main
What to do next: -

Save the following file as Hello.cs. cs is an extension to indicate C-sharp like .java for a Java Source File. You have to supply this extension while saving your file, otherwise the code will not compile correctly. The saved file will be of .cs.txt extension.

Compile the above Code by giving the following Command at the Command Prompt csc Hello.cs   
If there are compile errors then you will be prompted accordingly, otherwise you will be getting a command prompt with the copyright information. Keep in mind that the compiler generates MSIL.
   
Your next job is to execute the program to view the final Output. For that purpose you have to simply give Hello at the command Prompt. If everything goes on well, a message Hello C# will be printed on the Screen.

You can view the MSIL Code generated by any .NET Language with the help of an Utility called Intermediate Language Disassembler or shortly ILDASM. This utility will display the application's information in a tree like fashion. Since the contents of this file is read only, a Programmer or anybody accessing these files cannot make any modifications to the output generated by the Source Code.

To view the MSIL Code for the above Hello C# Program, open Hello.exe file from the ILDASM tool. In Windows 98, ME & NT this tool can be accessed via  start - programs - Microsoft .NET Framework SDK - Tools - IL Disassembler

Detailed Review of the above Program: -

I am giving below the process occurring to the source code, during the compilation and execution stages once again for your reference.

Compilation Stage: -

C# Compiler produces MSIL as output after compilation. It is itself a complete language and it is more or less similar to Assembly language. MSIL stands for Microsoft Intermediate Language. The same thing happens to any application written in any CLR Compliant Language like Visual Basic.NET, Visual C++.NET etc.

Execution Stage: -

The MSIL is then compiled into native CPU instructions by using JIT (Just in Time) compiler at the time of the program execution. The Source Code is recompiled and executed only after making any changes to it .

Now let us analyze the Hello C# Program as a whole. I am giving below the code once again for your reference. Please note that the line numbers are given for clarification and explanation and is not a part of the Source Code.

using System ;class Hello 
{public static void Main () 
{
Console.writeLine ("Hello C#"); 
} 
}//end of the main

Line Number wise Analysis
Line  - 1: - It is called as the namespace. Simply speaking, a namespace is a collection of .NET Classes similar to packages in Java.

Line - 2: - It is the class declaration similar to Java & C++

Line - 3: - This is the main method which is required in all C# applications.

Line - 4: - This code will print Hello C# onto the Console. Here Console is the class belonging to System namespace and writeLine is the static method belonging to Console Class.

Line - 5:- The Opening and Closing curly races are similar to that of C++/Java.