What is Microsoft.NET platform?

What is Microsoft.NET platform?
Microsoft .NET is a software development platform based on virtual machine based architecture. Dot net is designed from the scratch to support programming language independent application development. The entire .NET programs are independent of any particular operating system and physical hardware machine. They can run on any physical machine, running any operating system that contains the implementation of .NET Framework. The core component of the .NET framework is its Common Language Runtime (CLR), which provides the abstraction of execution environment (Physical machine and Operating System) and manages the overall execution of any of the .NET based program.



With dot NET, Microsoft introduces a completely new architecture for Windows applications (WinForm), Data Access (ADO.NET), Web Applications (ASP.NET), Windows components (Assemblies), Distributed Applications (.NET remoting), and above all the XML based Web Services. The famous figure for the representation of dot net is presented below:




What is the .NET framework?
The .NET framework is a collection of all the tools and utilities required to execute the .NET managed applications on a particular platform. The MS.NET framework includes the standard compilers (C#, VB.NET, J#, C++.NET, Jscript.NET), various utilities like (caspol, ngen, installutil, tlbimp, sn, asmreg, ildasm, etc), runtime environment (CLR), garbage collector, security manager, thread manager, assembly loader, just in time compilers, and the standard framework or base class libraries. It is important to realize that while the implementation of .Net applications is platform independent; the implementation of .NET framework is platform specific. In fact, it is this particular specific implementation of the .NET framework that makes the managed .NET applications platform independent.

What is the VB.NET and C# language comparisons?
VB.NET and C# both are integral part of the .NET framework. Both of the languages have a lot of similarities in language constructs and language design with minor differences in the syntax. C# is more like C++ and Java in its syntax while VB.NET lends its syntax from VB6 a great deal; although VB.NET can not be seen as the successor of Visual Basic at the level of overall language design and the vision of its creators.

The general conception is that most of the VB6 developers will upgrade to VB.NET while developers coming from Java or C++ to .NET are likely to go for C#. Since web developers for Windows using ASP are familiar with VB and VB Scripts, therefore, most of the web development with ASP.NET at the start is likely to be dominated by VB.NET; but after sometime C# will be able to attract at least half of these developers. Keeping technical side away, C++ and thus C# developers are generally paid more than those of VB developers. So, this might also be the factor for making C# the language of choice on .NET framework.

What is the difference between Console, Windows, Web applications and Web services?
Console applications are light weight programs run inside the command prompt (DOS) window. They are commonly used for test applications. Windows Applications are form based standard Windows desktop applications for common day to day tasks. Microsoft word is an example of a Windows application.

Web applications are programs that used to run inside some web server (e.g., IIS) to fulfill the user requests over the http. A typical example of web application is Hotmail and Google.

Web services are web applications that provide services to other applications over the internet. Google search engine’s web service, e.g., allows other applications to delegate the task of searching over the internet to Google web service and use the result produced by it in their own applications.

What is meant by language interoperability and language integration?
Prior to the introduction of .Net, the code written in one programming language is considered to be usable only in the programs written with the same programming languages. For example, an algorithm implemented in Perl programming language can not be reused in the programs written in the C++. At Windows platform, Microsoft introduced the standards for COM (Component Object Model) which allows components written in one programming language to be used in other programming language. In Java, JNI (Java Native Interface) is presented to use-up the code written in non-Java languages into Java programs. But both the standards (COM and JNI) are too complex and have their own limitations. They also don’t allow the language integration, which means that you can use the components written in other programming languages but you can’t extend the functionality of the components.

In Microsoft.Net, the code written in any programming language is compiled to the same Intermediate Language (Microsoft Intermediate Language - MSIL or Common Intermediate Language – CIL) and to same component standard (assembly). Hence, it is possible for developers to employ the language interoperability by using and extending the solution implemented by other developers which might be using different programming language provided developers at both end are using.Net compliant programming languages.

What is a .Net Assembly?
The .NET assembly is the standard for components developed with the Microsoft.NET. Dot NET assemblies may or may not be executable, i.e., they might exist as the executable (.exe) file or dynamic link library (DLL) file. All the .NET assemblies contain the definition of types, versioning information for the type, meta-data, and manifest. The designers of .NET have worked a lot on the component (assembly) resolution.

There are two kind of assemblies in .NET; private and shared. Private assemblies are simple and copied with each calling assemblies in the calling assemblies folder. Shared assemblies (also called strong named assemblies) are copied to a single location (usually the Global assembly cache). For all calling assemblies within the same application, the same copy of the shared assembly is used from its original location. Hence, shared assemblies are not copied in the private folders of each calling assembly. Each shared assembly has a four part name including its face name, version, public key token and culture information. The public key token and version information makes it almost impossible for two different assemblies with the same name or for two similar assemblies with different version to mix with each other.

An assembly can be a single file or it may consist of the multiple files. In case of multi-file, there is one master module containing the manifest while other assemblies exist as non-manifest modules. A module in .NET is a sub part of a multi-file .NET assembly. Assembly is one of the most interesting and extremely useful areas of .NET architecture along with reflections and attributes, but unfortunately very few people take interest in learning such theoretical looking topics.

What is a .Net Assembly?
The .NET assembly is the standard for components developed with the Microsoft.NET. Dot NET assemblies may or may not be executable, i.e., they might exist as the executable (.exe) file or dynamic link library (DLL) file. All the .NET assemblies contain the definition of types, versioning information for the type, meta-data, and manifest. The designers of .NET have worked a lot on the component (assembly) resolution.

There are two kind of assemblies in .NET; private and shared. Private assemblies are simple and copied with each calling assemblies in the calling assemblies folder. Shared assemblies (also called strong named assemblies) are copied to a single location (usually the Global assembly cache). For all calling assemblies within the same application, the same copy of the shared assembly is used from its original location. Hence, shared assemblies are not copied in the private folders of each calling assembly. Each shared assembly has a four part name including its face name, version, public key token and culture information. The public key token and version information makes it almost impossible for two different assemblies with the same name or for two similar assemblies with different version to mix with each other.

An assembly can be a single file or it may consist of the multiple files. In case of multi-file, there is one master module containing the manifest while other assemblies exist as non-manifest modules. A module in .NET is a sub part of a multi-file .NET assembly. Assembly is one of the most interesting and extremely useful areas of .NET architecture along with reflections and attributes, but unfortunately very few people take interest in learning such theoretical looking topics.

What are the differences between a .NET Assembly, a Windows DLL and a COM Component?
A Windows DLL contains library code to be used by any program running on Windows. A DLL may contain either structured or object oriented libraries.

COM (Component Object Model) is the component model based on the object oriented design, which means that the components represented by the COM component exists in the form of classes and objects implementing a standard specification defined by COM. COM components can be used by any program running on Windows Operating System; be it is written with VB, C++, Java or even some .NET compliant language like C# and VB.NET.

Dot NET assembly is the component standard specified by the .NET. Hence, dot net assemblies are understandable to only Microsoft.NET and can be used only in .NET managed applications.

What is the difference between an executable assembly and a class library?
An executable assembly exists as the .exe file while a class library exists as the .dll file. Executable assembly represent executable applications having some entry (e.g., Main() method in C#). A class library, on the other hand, contains components and libraries to be used inside various applications. A Class library can not be executed and thus it does not have any entry point.

What does one need to build or execute .NET applications?
To execute a standalone .NET application (Windows or Console application), one needs to first compile all its constituent assemblies and modules including the executable assembly. Once, the constituent assemblies are compiled, one needs to make sure that the target system contains the .NET framework. The application can now be executed by running its executable assembly (the .exe file). The executable assembly (.exe) is a Win32 executable that hosts the .Net CLR (Common Language Runtime), which exists as a COM component, in its process space and initializes it. Once the CLR is hosted and initialized, the starting point of the .NET executable assembly is passed to the hosted CLR which starts the execution of the program by translating and executing the parts of the program code.

What does it mean by managed code?
By managed code, it means that the complete life cycle and execution is managed by the .NET Common Language Runtime (CLR). The .NET CLR manages the memory on behalf of the managed code, performs garbage collection on the managed heap, perform assembly validation and assembly (component) resolution on behalf of the program. The CLR also maintains the security constraints applied to the managed code.

What is meant by un-safe code?
By un-safe code, it means that the managed program can access the memory address using pointers. There are two points to remember here;

* Un-safe code is different from un-managed as it is still managed by the CLR
* You still can not perform pointer arithmetic in un-safe code.


What is the difference between Unmanaged and Unsafe code?
Un-managed code runs outside the Common Language Runtime (CLR) control while the unsafe code runs inside the CLR’s control. Both un-safe and un-managed codes may use pointers and direct memory addresses.

What about the MS.NET standardization?
Microsoft has secured certification for both C# and CLI from ECMA and ISO/IEC as Industry standards. This is a very important step for Microsoft and .Net platform because this enhances the credibility of the newer .Net platform and allures a larger portion of technology industry into adopting .Net as their development platform. Several companies and government organizations only utilize ISO certified technologies; for example, in Australia anything ISO certified is also considered Australian standard according to the rules of the Australian government. Several academic institutions will now be interested in teaching standard C#. Another major outcome of having an open industry standard specification is .Net platform could be getting ported to other platforms like Linux and UNIX; best example is the Mono Project by Ximian- it is an open source implementation of .Net platform for UNIX and Linux based on ECMA approved Public Domain Specification of C# and CLI.

Microsoft submitted the specifications to ECMA, which in turn fast-tracked them through ISO. In doing so, Microsoft released all intellectual property in the core C#/CLI platform to the public domain. No one needs a license to implement C#/CLI. This will also help everybody in better understanding the implementations of C# and CLI which are at the core of .Net platform. However, the whole of .Net platform is not a Public domain standard- Microsoft still owns complete Intellectual property rights to several class libraries and API within the .Net platform. See

ECMA- http://www.ecma.org

ISO- http://www.iso.ch

Mono Project- http://www.mono-project.com/about/index.html

What about the implementation of .NET other than Microsoft.Net on Windows Operating System?
Microsoft has implemented .NET framework for all of its operating system suits (excluding MS Windows 95 and earlier) on all supported hardware platforms. For handheld and small devices, Microsoft has released a compact framework of .NET (http://msdn.microsoft.com/vstudio/device/compact.aspx ). But, there are various other implementations being developed on platforms other than Microsoft Windows. You can read the discussion on the portability of .NET at (See http://zdnet.com.com/2100-1107-960049.html)

The most popular implementation, after MS.NET, is the open source ‘Mono’ Project on Linux (See www.go-mono.com)

Microsoft has released almost all the source code of their .NET framework for FreeBSD and Mac OS under the title of Shared Source Common Language Infrastructure (SSCLI). Check out the SSCLI 1.0 release - which already builds on WindowsXP, FreeBSD, and Mac OS X 10.2, released under Microsoft's Shared Source Initiative. http://msdn.microsoft.com/net/sscli/ http://www.microsoft.com/resources/sharedsource/default.mspx

See also DotGNU Portable.NET http://www.southern-storm.com.au/portable_net.html

Also Microsoft has opened the .NET code to academics. See http://archive.infoworld.com/articles/hn/xml/02/03/27/020327hnshare.xml

What is the difference between traditional development and .NET development?
In traditional programming languages, the source code of a program is compiled to a specific platform’s assembly language and then machine language code. Later the library code required by the program is linked to it. Finally the operating system executes the program when desired by the user. The complete process is depicted in the following figure:



In the presence of dot net framework, a program is not compiled to the native machine executable code; rather it gets compiled to an intermediate language code called Microsoft Intermediate Language (MSIL) or Common Intermediate Language (CIL). The Dot Net Common Language Runtime (CLR) then converts this intermediate code at runtime to the machine executable code. The optimization is carried out at runtime. A program also does not call the operating system APIs directly; rather it delegates this task to the CLR which performs the desired operations on behalf of the program and returns the results of the operations back to the program. The CLR also performs the memory management, garbage collection, security and thread management on behalf of the program. Dot NET framework is shipped with the supporting object oriented framework of common code libraries, called the .NET Framework Class Library (FCL), to facilitate the common operations. Hence the .Net manages the overall execution of an application. This is the reason why the code running on .Net framework is sometimes called the managed code. The complete process is depicted in the following Figure. Note that only the CLR (and thus the .Net framework and not the user application) is interacting and coupled with the platform and operating system.