NET Framework 1.0

The old .NET Framework logo
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 ends 14 July 2009.[16]

[edit] .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.

[edit] 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 API changes.

[edit] .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 1 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.[17] Version 2.0 with Service Pack 2 requires Windows XP or Windows Server 2003.
It shipped with Windows Server 2003 R2 (not installed by default).

[edit] 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
Generics
Data Tables

[edit] .NET Framework 3.0
.NET Framework 3.0, formerly called WinFX,[18] 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.[19] 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.

[edit] .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. In addition, it installs .NET Framework 2.0 SP1, .NET Framework 2.0 SP2 (with 3.5 SP1) and .NET Framework 3.0 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.[20]
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.[1]

[edit] 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.[21]
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[21]
Peer-to-peer networking stack, including a managed PNRP resolver[22]
Managed wrappers for Windows Management Instrumentation and Active Directory APIs[23]
Enhanced WCF and WF runtimes, which let WCF work with POX and JSON data, and also expose WF workflows as WCF services.[24] WCF services can be made stateful using the WF persistence model.[21]
Support for HTTP pipelining and syndication feeds.[24]
ASP.NET AJAX is included
New System.CodeDom namespace.

[edit] 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,[25] 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.
There is also a new variant of the .NET Framework, called the ".NET Framework Client Profile", which at 28 MB is a lot smaller than the full framework and only installs components that are the most relevant to desktop applications.[26] However, the Client Profile amounts to this size only if using the online installer. When using the off-line installer, the download size is still 250 MB.[27]

[edit] .NET Framework 4.0

This article or section contains information about scheduled or expected future software.The content may change as the software release approaches and more information becomes available.

Microsoft announced the .NET Framework 4.0 on 29 September 2008. While full details about its feature set have yet to be released, some general information regarding the company's plans have been made public. Some focus of this release are:
Improve support for parallel computing, which target multi-core or distributed systems.[28] To this end, they plan to include technologies like PLINQ (Parallel LINQ),[29] a parallel implementation of the LINQ engine, and Task Parallel Library, which exposes parallel constructs via method calls.[30]
Full support for IronPython, IronRuby, and F#.[31]
Support for a subset of the .NET Framework and ASP.NET with the "Server Core" variant of Windows Server 2008 R2.[32]
Support for Code Contracts.

[edit] .NET vs. Java and Java EE
See also: Comparison of the Java and .NET platforms and Comparison of C# and Java
The CLI and .NET languages such as C# and VB have many similarities to Sun's JVM and Java. They are strong competitors. Both are based on a virtual machine model that hides the details of the computer hardware on which their programs run. Both use their own intermediate byte-code, Microsoft calling theirs Common Intermediate Language (CIL; formerly MSIL) and Sun calling theirs Java bytecode. On .NET the byte-code is always compiled before execution, either Just In Time (JIT) or in advance of execution using the ngen.exe utility. With Java the byte-code is either interpreted, compiled in advance, or compiled JIT. Both provide extensive class libraries that address many common programming requirements and address many security issues that are present in other approaches. The namespaces provided in the .NET Framework closely resemble the platform packages in the Java EE API Specification in style and invocation.
.NET in its complete form (i.e., Microsoft's implementation, described in the Standardization and licensing section of this article) can only be installed on computers running a Microsoft Windows operating system[33][34][35] whereas Java in its entirety can be installed on computers running any one of a variety of operating systems such as Linux, Solaris or Windows.[36] From its beginning .NET has supported multiple programming languages and at its core remains platform agnostic and standardized so that other vendors can implement it on other platforms (although Microsoft's implementation only targets Windows, Windows CE, and Xbox platforms). The Java platform was initially built to support only the Java language on many operating system platforms under the slogan "Write once, run anywhere." Other programming languages have been implemented on the Java Virtual Machine[37] but are less widely used (see JVM languages).
Sun's reference implementation of Java (including the class library, the compiler, the virtual machine, and the various tools associated with the Java Platform) is open source under the GNU GPL license with Classpath exception.[38] The source code for the .NET framework base class library is available for reference purposes only under the Microsoft Reference License.[39][40]
The third-party Mono Project, sponsored by Novell, has been developing an open source implementation of the ECMA standards that define the .NET Framework, as well as most of the other non-ECMA standardized libraries in Microsoft's .NET. The Mono implementation is meant to run on Linux, Solaris, Mac OS X, BSD, HP-UX, and Windows platforms. Mono includes the CLR, the class libraries, and compilers for C# and VB.NET. The current version supports all the APIs in version 2.0 of Microsoft's .NET. Full support exists for C# 3.0 LINQ to Objects and LINQ to Xml.[41]

[edit] Criticism
Some concerns and criticism relating to .NET include:
Applications running in a managed environment tend to require more system resources than similar applications that access machine resources more directly.
As MSIL can be more easily reverse-engineered (than native code), there is concern over possible loss of trade secrets and the bypassing of license control mechanisms. Many obfuscation techniques already developed can help to prevent this; Microsoft's Visual Studio 2005 (and newer) includes such a tool.
In a managed environment the regularly occurring garbage collection for reclaiming memory suspends execution of the application for an unpredictable lapse of time (typically no more than a few milliseconds, but in memory-constrained systems can be much longer). This makes such environments unsuitable for some applications such as those that must respond to events with predictable timing (see real-time computing).
Since the framework is not pre-installed on older versions of Windows an application that requires it must verify that it is present, and if it is not, guide the user to install it. This requirement may deter some from using the application as the downloads are many megabytes in size.
Newer versions of the framework (3.5 and up) are not pre-installed in versions of Windows below Windows 7. Some developers have expressed concerns about the large size (around 54 MB for end-users with .NET 3.0, 197 MB with .NET 3.5, and 250 MB with .NET 3.5 SP1) and reliability of .NET framework runtime installers for end-users. The first service pack for version 3.5 mitigates this concern by offering a lighter-weight client-only subset of the full .NET Framework. Two significant limitations should be noted, though[42]. Firstly, the client-only subset is only an option on an existing Windows XP SP2 system that currently has no other version of the .NET framework installed. In all other scenarios, the client-only installer will install the full version of the .NET Framework 3.5 SP1. Secondly, the client-only framework does not have a 64-bit option.
The .NET framework currently does not provide support for calling Streaming SIMD Extensions (SSE) via managed code. However, Mono has provided support for SIMD Extensions as of version 2.2 within the Mono.Simd namespace; Mono's lead developer Miguel de Icaza has expressed hope that this SIMD support will be adopted by the CLR ECMA standard.[43] Streaming SIMD Extensions have been available in CPUs since the introduction of the Pentium III.

[edit] Alternative implementations
The Microsoft .NET Framework is the predominant implementation of .NET technologies. Other implementations for parts of the framework exist. Since the runtime engine is described by an ECMA/ISO specification, other implementations of it are unencumbered by patent issues. It is more difficult to develop alternatives to the base class library (BCL), which is not described by an open standard and may be subject to copyright restrictions. Additionally, parts of the BCL have Windows-specific functionality and behavior, so implementation on non-Windows platforms can be problematic.
Some alternative implementations of parts of the framework are listed here.
Microsoft's Shared Source Common Language Infrastructure is a non-free shared source implementation of the CLR component of the .NET Framework. However, the last version only runs on Microsoft Windows XP SP2, and does not contain all features of version 2.0 of the .NET Framework.
Portable.NET (part of DotGNU) provides an implementation of the Common Language Infrastructure (CLI), portions of the .NET Base Class Library (BCL), and a C# compiler. It supports a variety of CPUs and operating systems.
Microsoft's .NET Micro Framework is a .NET platform for extremely resource-constrained devices. It includes a small version of the .NET CLR and supports development in C# and debugging (in an emulator or on hardware), both using Microsoft Visual Studio. It also features a subset of the .NET base class libraries (about 70 classes with about 420 methods), a GUI framework loosely based on Windows Presentation Foundation, and additional libraries specific to embedded applications.
Mono is an implementation of the CLI and portions of the .NET Base Class Library (BCL), and provides additional functionality. It is dual-licensed under free software and proprietary software licenses. Mono is being developed by Novell, Inc. It includes support for ASP.NET, ADO.NET, and evolving support for Windows Forms libraries. It also includes a C# compiler, and a VB.NET compiler is in pre-beta form.
CrossNet is an implementation of the CLI and portions of the .NET Base Class Library (BCL). It is free software. It parses .NET assemblies and generates unmanaged C++ code that can be compiled and linked within any ANSI C++ application on any platform.
.NET for Symbian .NET Compact Framework implementation for Symbian (S60)