platform for developing modern applications.
• Rich Functionality out of the box
.NET framework provides a rich set of functionality out of the box. It contains
hundreds of classes that provide variety of functionality ready to use in your
applications. This means that as a developer you need not go into low level details
of many operations such as file IO, network communication and so on.
• Easy development of web applications
ASP.NET is a technology available on .NET platform for developing dynamic
and data driven web applications. ASP.NET provides an event driven
programming model (similar to Visual Basic 6 that simplify development of web
pages (now called as web forms) with complex user interface. ASP.NET server
controls provide advanced user interface elements (like calendar and grids) that
save lot of coding from programmer’s side.
• OOPs Support
The advantages of Object Oriented programming are well known. .NET provides
a fully object oriented environment. The philosophy of .NET is – “Object is
mother of all.” Languages like Visual Basic.NET now support many of the OO
features that were lacking traditionally. Even primitive types like integer and
characters can be treated as objects – something not available even in OO
languages like C++.
• Multi-Language Support
Generally enterprises have varying skill sets. For example, a company might have
people with skills in Visual Basic, C++, and Java etc. It is an experience that
whenever a new language or environment is invented existing skills are outdated.
This naturally increases cost of training and learning curve. .NET provides
something attractive in this area. It supports multiple languages. This means that
if you have skills in C++, you need not throw them but just mould them to suit
.NET environment. Currently four languages are available right out of the box
namely – Visual Basic.NET, C# (pronounced as C-sharp), Jscript.NET and
Managed C++ (a dialect of Visual C++). There are many vendors that are
working on developing language compilers for other languages (20+ language
compilers are already available). The beauty of multi language support lies in the
fact that even though the syntax of each language is different, the basic
capabilities of each language remain at par with one another.
• Multi-Device Support
Modern lift style is increasingly embracing mobile and wireless devices such as
PDAs, mobiles and handheld PCs. . . .NET provides promising platform for
programming such devices. .NET Compact Framework and Mobile Internet
Toolkit are step ahead in this direction.
• Automatic memory management
While developing applications developers had to develop an eye on system
resources like memory. Memory leaks were major reason in failure of
applications. .NET takes this worry away from developer by handling memory on
its own. The garbage collector takes care of freeing unused objects at appropriate
intervals.
• Compatibility with COM and COM+
Before the introduction of .NET, COM was the de-facto standard for
componentized software development. Companies have invested lot of money and
efforts in developing COM components and controls. The good news is – you can
still use COM components and ActiveX controls under .NET. This allows you to
use your existing investment in .NET applications. .NET still relies on COM+ for
features like transaction management and object pooling. In fact it provides
enhanced declarative support for configuring COM+ application right from your
source code. Your COM+ knowledge still remains as a valuable asset.
• No more DLL Hell
If you have worked with COM components, you probably are aware of “DLL
hell”. DLL conflicts are a common fact in COM world. The main reason behind
this was the philosophy of COM – “one version of component across machine”.
Also, COM components require registration in the system registry. .NET ends this
DLL hell by allowing applications to use their own copy of dependent DLLs.
Also, .NET components do not require any kind of registration in system registry.
• Strong XML support
Now days it is hard to find a programmer who is unaware of XML. XML has
gained such a strong industry support that almost all the vendors have released
some kind of upgrades or patches to their existing software to make it “XML
compatible”. Currently, .NET is the only platform that has built with XML right
into the core framework. .NET tries to harness power of XML in every possible
way. In addition to providing support for manipulating and transforming XML
documents, .NET provides XML web services that are based on standards like
HTTP, XML and SOAP.
• Ease of deployment and configuration
Deploying windows applications especially that used COM components were
always been a tedious task. Since .NET does not require any registration as such,
much of the deployment is simplified. This makes XCOPY deployment viable.
Configuration is another area where .NET – especially ASP.NET – shines over
traditional languages. The configuration is done via special files having special
XML vocabulary. Since, most of the configuration is done via configuration files,
there is no need to sit in front of actual machine and configure the application
manually. This is more important for web applications; simply FTPing new
configuration file makes necessary changes.
• Security
Windows platform was always criticized for poor security mechanisms. Microsoft
has taken great efforts to make .NET platform safe and secure for enterprise
applications. Features such as type safety, code access security and role based
authentication make overall application more robust and secure.
The next layer up in the framework is called the .NET Class Framework also referred
as .NET base class library. The .NET Class Framework consists of several thousand
type definitions, where each type exposes some functionality. All in all, the CLR and
the .NET Class Framework allow developers to build the following kinds of
applications:
• Web Services. Components that can be accessed over the Internet very easily.
• Web Forms. HTML based applications (Web Sites).
• Windows Forms. Rich Windows GUI applications. Windows form applications can
take advantage of controls, mouse and keyboard events and can talk directly to
the underlying OS.
• Windows Console Applications. Compilers, utilities and tools are typically
implemented as console applications.
• Windows Services. It is possible to build service applications controllable via the
Windows Service Control Manager (SCM) using the .NET Framework.
• Component Library. .NET Framework allows you to build stand-alone components
(types) that may be easily incorporated into any of the above mentioned
application types.
The Common Language Runtime (CLR)........
At the base is the CLR. It is considered as the heart of the .NET framework. .NET
applications are compiled to a common language known as Microsoft Intermediate
Language or “IL”. The CLR, then, handles the compiling the IL to machine language,
at which point the program is executed.
The CLR environment is also referred to as a managed environment, in which
common services, such as garbage collection and security, are automatically
provided.
More information on CLR is available at
as .NET base class library. The .NET Class Framework consists of several thousand
type definitions, where each type exposes some functionality. All in all, the CLR and
the .NET Class Framework allow developers to build the following kinds of
applications:
• Web Services. Components that can be accessed over the Internet very easily.
• Web Forms. HTML based applications (Web Sites).
• Windows Forms. Rich Windows GUI applications. Windows form applications can
take advantage of controls, mouse and keyboard events and can talk directly to
the underlying OS.
• Windows Console Applications. Compilers, utilities and tools are typically
implemented as console applications.
• Windows Services. It is possible to build service applications controllable via the
Windows Service Control Manager (SCM) using the .NET Framework.
• Component Library. .NET Framework allows you to build stand-alone components
(types) that may be easily incorporated into any of the above mentioned
application types.
The Common Language Runtime (CLR)........
At the base is the CLR. It is considered as the heart of the .NET framework. .NET
applications are compiled to a common language known as Microsoft Intermediate
Language or “IL”. The CLR, then, handles the compiling the IL to machine language,
at which point the program is executed.
The CLR environment is also referred to as a managed environment, in which
common services, such as garbage collection and security, are automatically
provided.
More information on CLR is available at
The next layer up in the framework is called the .NET Class Framework also referred
as .NET base class library. The .NET Class Framework consists of several thousand
type definitions, where each type exposes some functionality. All in all, the CLR and
the .NET Class Framework allow developers to build the following kinds of
applications:
• Web Services. Components that can be accessed over the Internet very easily.
• Web Forms. HTML based applications (Web Sites).
• Windows Forms. Rich Windows GUI applications. Windows form applications can
take advantage of controls, mouse and keyboard events and can talk directly to
the underlying OS.
• Windows Console Applications. Compilers, utilities and tools are typically
implemented as console applications.
• Windows Services. It is possible to build service applications controllable via the
Windows Service Control Manager (SCM) using the .NET Framework.
• Component Library. .NET Framework allows you to build stand-alone components
(types) that may be easily incorporated into any of the above mentioned
application types.
The Common Language Runtime (CLR)........
At the base is the CLR. It is considered as the heart of the .NET framework. .NET
applications are compiled to a common language known as Microsoft Intermediate
Language or “IL”. The CLR, then, handles the compiling the IL to machine language,
at which point the program is executed.
The CLR environment is also referred to as a managed environment, in which
common services, such as garbage collection and security, are automatically
provided.
More information on CLR is available at
as .NET base class library. The .NET Class Framework consists of several thousand
type definitions, where each type exposes some functionality. All in all, the CLR and
the .NET Class Framework allow developers to build the following kinds of
applications:
• Web Services. Components that can be accessed over the Internet very easily.
• Web Forms. HTML based applications (Web Sites).
• Windows Forms. Rich Windows GUI applications. Windows form applications can
take advantage of controls, mouse and keyboard events and can talk directly to
the underlying OS.
• Windows Console Applications. Compilers, utilities and tools are typically
implemented as console applications.
• Windows Services. It is possible to build service applications controllable via the
Windows Service Control Manager (SCM) using the .NET Framework.
• Component Library. .NET Framework allows you to build stand-alone components
(types) that may be easily incorporated into any of the above mentioned
application types.
The Common Language Runtime (CLR)........
At the base is the CLR. It is considered as the heart of the .NET framework. .NET
applications are compiled to a common language known as Microsoft Intermediate
Language or “IL”. The CLR, then, handles the compiling the IL to machine language,
at which point the program is executed.
The CLR environment is also referred to as a managed environment, in which
common services, such as garbage collection and security, are automatically
provided.
More information on CLR is available at
Microsoft intermediate language (MSIL), which is a CPU-independent set of
instructions that can be efficiently converted to native code. MSIL includes
instructions for loading, storing, initializing, and calling methods on objects, as well
as instructions for arithmetic and logical operations, control flow, direct memory
access, exception handling, and other operations. Before code can be executed, MSIL
must be converted to CPU-specific code by a just in time (JIT) compiler. Because the
runtime supplies one or more JIT compilers, for each computer architecture it
supports, the same set of MSIL can be JIT-compiled and executed on any supported
architecture.
When a compiler produces MSIL, it also produces metadata. The MSIL and metadata
are contained in a portable executable (PE file) that is based on and extends the
published Microsoft PE and Common Object File Format (COFF) used historically for
executable content. This file format, which accommodates MSIL or native code as
well as metadata, enables the operating system to recognize common language
runtime images. The presence of metadata in the file along with the MSIL enables
your code to describe itself, which means that there is no need for type libraries or
Interface Definition Language (IDL). The runtime locates and extracts the metadata
from the file as needed during execution.
does nothing but displays a “HelloWorld” string in the screen. Taking this simple
program we will try to figure out how .NET framework delivers a successful
HelloWorld.exe. Well to write such a complex program we will go for our favorite editor,
the choice is unanimous, it’s “Notepad”.
'This is the famous HelloWorld Program written using VB.NET
Namespace HelloWorldSample
'Definition of the Class
Public Class HelloWorld
'entry point method for the Class
Public Shared Sub Main()
System.Console.WriteLine("HelloWorld")
End Sub
'end of Class Declaration
End Class
'end of the Class Module
'end of namespace
End Namespace
Now let us spend sometime in examining the HelloWorld program to find out what’s new
in writing code through any .NET language.
The lines in the program that starts with a ‘(single quote) are comment entries like in
other programming languages which are excluded in the compilation process. Like VB
the way in which comment entries are represented remains the same in VB.NET.
Namespace HelloWorldSample - The keyword “Namespace” is new to some
programmers who are not familiar with C++.
‘Namespace’ – a keyword in .NET is used to avoid name collisions i.e. For example, you
develop a library which has a class named “File” and you use some other library which
also has a class named “File”, in those cases there are chances of name collision. To
avoid this you can give a namespace name for your class, which should be meaningful. It
is always better to follow the syntax (MS Recommended) given below while giving
names for your namespaces
CompanyName.TechnologyName
However the hierarchy can be extended based on the implementation of the classes in the
library.
Public Class HelloWorld - This is the class declaration in VB.NET; the interesting thing
for VB developers is that VB.NET is a fully object-oriented language (so everything is a
Class here) . The class always ends with an “End Class”.
‘Public’ - is the modifier to determine the scope of the class (for other modifiers refer
.NET framework SDK documentation or later parts of this tutorial). HelloWorld is the
class name given for the class. Consumers of the class will be accessing through this
name only
Public Shared Sub Main () - This is called as the entry point function because the
runtime after loading your applications searches for an entry point from which the actual
execution starts. C/C++ programmers will find this method very familiar (VB
Programmers remember Sub Main). All Applications (exe) must have a definition for the
Main Method. Try removing the Main method from your application and the compiler
will complain that "No Start Point Defined". This means that the Main Method is the
starting point of any application, in other words When you execute your Application
"Main" method is called first automatically.
'Public' - This is the Access modifier for the Method. Since the Main method should be
accessible to everyone in order for the .NET Runtime to be able to call it automatically it
is always defined as public.
'Shared' - indicates that the method is a Class Method. Hence it can be called without
making an instance of the class first.
Now its time to compile and execute this complex program. To compile the above piece
of code you can use VB.NET compiler. To run the VB.NET compiler make sure you set
your path variable to point to the place where your VB.NET compiler is available. (To
set a new value in the path variable, go to control panel and double click System icon,
then choose advanced tab and click Environment Variables button to add or edit the
environmental variables)
Figure shows compilation of the HelloWorld program for VB.NET
The compiler used here is “vbc”, which is a visual basic .net compiler accepts the source
file “HelloWorld.vb” compiles the same to produce a program that’s not true executable,
instead it generates something called assembly. Here the VB.NET compiler produces a
Managed Code/Intermediate Language (MSIL) format that uses instructions which are
CPU-independent.
