.NET Framework 1.0
 .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 April 3, 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.
 Changes since 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.
 .NET Framework 2.0
- The 2.0 Redistributable Package can be downloaded for free from Microsoft, and was published on 2006-01-22.
- 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 is the last version with support for Windows 2000, Windows 98 and Windows Me.
- It shipped with Windows Server 2003 R2 (not installed by default).
 Changes since 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.
 .NET Framework 3.0
.NET Framework 3.0, formerly called WinFX,  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
- This version of the framework uses version 2.0 of the CLR (the same model as the use of CLR 2.0 in .NET Framework 3.0). However, it installs .NET Framework 2.0 SP1, which adds some methods and properties, required for .NET Framework 3.5 features such as LINQ, to the BCL classes in .NET Framework 2.0. These changes do not affect applications written for version 2.0 of the .NET Framework.
- Full support for .NET Framework 3.5 project types, as well as targeting .NET Framework 3.5 in builds, is included in Visual Studio 2008.
- The source code of the Base Class Library in this release will be released under Microsoft Reference License.
- .NET Framework 3.5 SP1, codenamed "Arrowhead", will enhance support for occasionally connected applications. and provide built-in support for the Microsoft ASP.NET MVC Framework.
- As with .NET Framework 1.0 and 2.0, a new .NET Compact Framework 3.5 will be released in tandem with this update, to provide e.g. LINQ, HTTP compression, and improved audio support for mobile devices.
- Officially Released To Manufacturing (RTM) on 19 November 2007.
- New language features in C# 3.0 and VB.NET 9.0 compiler
- Adds support for expression trees and lambda methods
- Extension methods
- 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 WMI and Active Directory APIs
- Enhancements to the WCF and WF runtimes that let WCF work with POX and JSON data, as well as expose WF workflows as WCF services.
- Support for HTTP pipelining and syndication feeds.
- ASP.NET AJAX is included