Microsoft started development on the .NET Framework in the late 1990s originally under the name of Next Generation Windows Services (NGWS). By late 2000 the first beta versions of .NET 1.0 were released.

.NET Framework 1.0

This is the first release of the .NET Framework, released on 13 February 2002 and available for Windows 98, Me, NT 4.0, 2000, and XP. Mainstream support by Microsoft for this version ended 10 July 2007, and extended support ended 14 July 2009.



.NET Framework 1.1
This is the first major .NET Framework upgrade. It is available on its own as a redistributable package or in a software development kit, and was published on 3 April 2003. It is also part of the second release of Microsoft Visual Studio .NET (released as Visual Studio .NET 2003). This is the first version of the .NET Framework to be included as part of the Windows operating system, shipping with Windows Server 2003. Mainstream support for .NET Framework 1.1 ended on 14 October 2008, and extended support ends on 8 October 2013. Since .NET 1.1 is a component of Windows Server 2003, extended support for .NET 1.1 on Server 2003 will run out with that of the OS - currently 14 July 2015.


Changes in 1.1 on comparison with 1.0

• Built-in support for mobile ASP.NET controls. Previously available as an add-on for .NET Framework, now part of the framework.
• Security changes - enable Windows Forms assemblies to execute in a semi-trusted manner from the Internet, and enable Code Access Security in ASP.NET applications.
• Built-in support for ODBC and Oracle databases. Previously available as an add-on for .NET Framework 1.0, now part of the framework.
• .NET Compact Framework - a version of the .NET Framework for small devices.
• Internet Protocol version 6 (IPv6) support.
• Numerous changes.

.NET Framework 2.0
Released with Visual Studio 2005, Microsoft SQL Server 2005, and BizTalk 2006.

• The 2.0 Redistributable Package can be downloaded for free from Microsoft, and was published on 22 January 2006.
• The 2.0 Software Development Kit (SDK) can be downloaded for free from Microsoft.
• It is included as part of Visual Studio 2005 and Microsoft SQL Server 2005.
• Version 2.0 without any Service Pack is the last version with support for Windows 98 and Windows Me. Version 2.0 with Service Pack 2 is the last version with official support for Windows 2000 although there have been some unofficial workarounds published online to use a subset of the functionality from Version 3.5 in Windows 2000.Version 2.0 with Service Pack 2 requires Windows 2000 with SP4 plus KB835732 or KB891861 update, Windows XP with SP2 or later and Windows Installer 3.1 (KB893803-v2) although you can just copy the directories "Microsoft.NET" and "assembly" (located in %SYSTEMROOT%) from the computer where the .NET Framework is installed, also mscoree.dll, msvc*80.dll, gdiplus.dll in "%SYSTEMROOT%\System32" and add value to the registry "HKLM\SOFTWARE\Microsoft\.NETFramework", parameter "InstallRoot" with value "C:\\WINDOWS\\Microsoft.NET\\Framework\\".
• It shipped with Windows Server 2003 R2 (not installed by default).

 Changes in 2.0 in comparison with 1.1

• Numerous API changes.
• A new hosting API for native applications wishing to host an instance of the .NET runtime. The new API gives a fine grain control on the behavior of the runtime with regards to multithreading, memory allocation, assembly loading and more (detailed reference). It was initially developed to efficiently host the runtime in Microsoft SQL Server, which implements its own scheduler and memory manager.
• Full 64-bit support for both the x64 and the IA64 hardware platforms.
• Language support for generics built directly into the .NET CLR.
• Many additional and improved ASP.NET web controls.
• New data controls with declarative data binding.
• New personalization features for ASP.NET, such as support for themes, skins and webparts.
• .NET Micro Framework - a version of the .NET Framework related to the Smart Personal Objects Technology initiative.
• Partial classes
• Anonymous methods
• Data Tables
• Generics

.NET Framework 3.0
.NET Framework 3.0, formerly called WinFX,was released on 21 November 2006. It includes a new set of managed code APIs that are an integral part of Windows Vista and Windows Server 2008 operating systems. It is also available for Windows XP SP2 and Windows Server 2003 as a download. There are no major architectural changes included with this release; .NET Framework 3.0 uses the Common Language Runtime of .NET Framework 2.0.Unlike the previous major .NET releases there was no .NET Compact Framework release made as a counterpart of this version.

.NET Framework 3.0 consists of four major new components:

• Windows Presentation Foundation (WPF), formerly code-named Avalon; a new user interface subsystem and API based on XML and vector graphics, which uses 3D computer graphics hardware and Direct3D technologies. See WPF SDK for developer articles and documentation on WPF.
• Windows Communication Foundation (WCF), formerly code-named Indigo; a service-oriented messaging system which allows programs to interoperate locally or remotely similar to web services.
• Windows Workflow Foundation (WF) allows for building of task automation and integrated transactions using workflows.
• Windows CardSpace, formerly code-named InfoCard; a software component which securely stores a person's digital identities and provides a unified interface for choosing the identity for a particular transaction, such as logging in to a website.

.NET Framework 3.5
Version 3.5 of the .NET Framework was released on 19 November 2007, but it is not included with Windows Server 2008. As with .NET Framework 3.0, version 3.5 uses the CLR of version 2.0. Which means it's not a complete new framework, but just an extension of 2.0, and it can't run without it. In addition, it installs .NET Framework 2.0 SP1, (installs .NET Framework 2.0 SP2 with 3.5 SP1) and .NET Framework 3.0 SP1 (installs .NET Framework 3.0 SP2 with 3.5 SP1), which adds some methods and properties to the BCL classes in version 2.0 which are required for version 3.5 features such as Language Integrated Query (LINQ). These changes do not affect applications written for version 2.0, however.
As with previous versions, a new .NET Compact Framework 3.5 was released in tandem with this update in order to provide support for additional features on Windows Mobile and Windows Embedded CE devices.

The source code of the Base Class Library in this version has been partially released (for debugging reference only) under the Microsoft Reference Source License.


Changes since version 3.0

• New language features in C# 3.0 and VB.NET 9.0 compiler
• Adds support for expression trees and lambda methods
• Extension methods
• Expression trees to represent high-level source code at runtime.
•  Anonymous types with static type inference
• Language Integrated Query (LINQ) along with its various providers
• LINQ to Objects
• LINQ to XML
• LINQ to SQL
• Paging support for ADO.NET
• ADO.NET synchronization API to synchronize local caches and server side datastores
• Asynchronous network I/O API.
• Peer-to-peer networking stack, including a managed PNRP resolver
• Managed wrappers for Windows Management Instrumentation and Active Directory APIs
• Enhanced WCF and WF runtimes, which let WCF work with POX and JSON data, and also expose EF workflows as WCF services. WCF services can be made stateful using the WF persistence model.
• Support for HTTP pipelining and syndication feeds.
• ASP.NET AJAX is included

Service Pack 1

The .NET Framework 3.5 Service Pack 1 was released on 11 August 2008. This release adds new functionality and provides performance improvements under certain conditions, especially with WPF where 20-45% improvements are expected. Two new data service components have been added, the ADO.NET Entity Framework and ADO.NET Data Services. Two new assemblies for web development, System.Web.Abstraction and System.Web.Routing, have been added; these are used in the ASP.NET MVC Framework and, reportedly, will be utilized in the future release of ASP.NET Forms applications. Service Pack 1 is included with SQL Server 2008 and Visual Studio 2008 Service Pack 1.It also featured a new set of controls called "Visual Basic Power Packs" which brought back Visual Basic controls such as "Line" and "Shape".

.NET Framework 3.5 SP1 Client Profile

For the .NET Framework 3.5 SP1 there is also a new variant of the .NET Framework, called the ".NET Framework Client Profile", which at 28 MB is significantly smaller than the full framework and only installs components that are the most relevant to desktop applications. However, the Client Profile amounts to this size only if using the online installer on Windows XP SP2 when no other .NET Frameworks are installed. When using the off-line installer or any other OS, the download size is still 250 MB.


.NET Framework 4

Microsoft announced the .NET Framework 4 on 29 September 2008. The Public Beta was released on 20 May 2009.[3] Some focuses of this release are:

• Parallel Extensions to improve support for parallel computing, which target multi-core or distributed systems.To this end, they plan to include technologies like PLINQ (Parallel LINQ),a parallel implementation of the LINQ engine, and Task Parallel Library, which exposes parallel constructs via method calls.
• New Visual Basic and C# language features, such as statement lambdas, implicit line continuations, dynamic dispatch, named parameters, and optional parameters.
• Full support for IronPython, IronRuby, and F#.
• Support for a subset of the .NET Framework and ASP.NET with the "Server Core" variant of Windows Server 2008 R2.
• Support for Code Contracts.
• Inclusion of the Oslo modelling platform, along with the M programming language.

On 28 July 2009, a second release of the .NET Framework 4 beta was made available with experimental software transactional memory support.[35] Whether this functionality will be available in the final version of the framework has not been confirmed.

On 19 October 2009, Microsoft released Beta 2 of the .NET Framework 4.[36] At the same time, Microsoft announced the expected launch date for .NET Framework 4 as the 22 March 2010.[36] This launch date has subsequently been delayed to April 12, 2010.[37]

In conjunction with .NET Framework 4, Microsoft will offer a set of enhancements, codenamed Dublin, for Windows Server 2008 application server capabilities.[38][39] Dublin will extend IIS to be a "standard host" for applications that use either WCF or WF.[39]

There are lot of new features in ASP.NET 4.0 like html, jscript snippets, new development profiles, generate form usage, enablePersistedSelection, web.config transformation, compression enabling for session values etc.