The Windows® SDK, which includes content for the Microsoft® .NET Framework 3.0, provides you with a set of managed Application Programming Interfaces (APIs), documentation, samples, and tools that allow you to create a wide variety of applications for Windows. At a high level, .NET Framework 3.0 consists of these basic components:

.NET Framework

Microsoft® Windows® Communication Foundation

Microsoft® Windows® Presentation Foundation

Microsoft® Windows® Workflow Foundation

.NET Framework
The core API contains classes that are shared by all types of .NET Framework 3.0 applications. For more information, see .NET Framework Conceptual Overview. They are largely part of the System namespace as well as descendants such as System.Collections. The .NET Framework APIs include support for:

Basic value and reference types, such as Int32, String, and Uri

Collections and Data Structures

Data

Graphics and Drawing

Input/Output

Basic networking

Security

Threading and runtime services

The .NET Framework also provides support for creating Web applications and Windows applications.

ASP.NET is a unified Web platform that provides all the services needed to build enterprise-class Web applications. The classes that make up the API are largely part of the System.Web namespace, or its descendants. For details, see ASP.NET Web Applications.

Windows Forms is a platform for developing Windows client applications. A Windows Forms application can also act as the local user interface in a multi-tier distributed solution. Windows Forms extends the core API with a clear, object-oriented, extensible set of classes that enable you to develop rich Windows client applications. The classes that make up the API are largely part of the System.Windows.Forms namespace, or its descendants. For details, see Windows Forms.

Windows Communication Foundation
Windows Communication Foundation is the new service-oriented communications infrastructure built on top of web services protocols. The advanced web service support in Windows Communication Foundation provides interoperable secure, reliable, and transacted messaging. For details, see What is Windows Communication Foundation?

The Windows Communication Foundation service-oriented programming model is built on the .NET Framework and radically simplifies development of connected systems. It unifies a broad array of distributed systems capabilities in a composable, extensible architecture that supports multiple transports, messaging patterns, encodings, network topologies, and hosting models. It is the next version of several existing products: ASP.NET’s web methods (“ASMX”) and Microsoft Web Services Enhancements for Microsoft .NET (WSE), .NET Remoting, Enterprise Services, and System.Messaging.

The classes that make up the Windows Communication Foundation API are largely part of the System.ServiceModel namespace and its sub-namespaces. Windows Communication Foundation supports a variety of scenarios, including:

One-way and duplex messaging

Synchronous and asynchronous remote procedure calls

Callbacks

Sessions

Multi-contract services

Transport- and message-based security, reliability, and ordered delivery

Queued messaging

Transaction support

Windows Presentation Foundation
Windows Presentation Foundation is Microsoft’s unified presentation subsystem for Windows. It consists of a display engine and a set of managed classes that allow you to create rich, visually-stunning applications. Windows Presentation Foundation also introduces XAML, which allows you to use an XML-based model to declaratively manipulate the Windows Presentation Foundation object model. To learn more, see Windows Presentation Foundation.

The classes that make up the API are largely part of the System.Windows namespace or its descendants. The primary components are:

An application model with support for navigation, windows, and dialog boxes

UI data binding

A rich set of extensible layout and control objects

2D and 3D graphics

Animation

Media

Documents

Windows Workflow Foundation
Windows Workflow Foundation is a new workflow development platform built on the .NET Framework.

Windows Workflow Foundation provides a programming model for developing and executing a wide variety of stateful, long-running, persistent workflow applications.

Windows Workflow Foundation provides out-of-the-box workflow functionality that for easily developing workflow-based applications such as document management, commercial page flow, IT management, and various line-of-business applications.

Applications can load the workflow engine and plug a variety of runtime service components into it. Windows Workflow Foundation is highly extensible, so you can create your own custom components to address your particular business concerns.

Windows Workflow Foundation also offers ASP.NET support to make it easy for you to build and execute workflows that run in the Internet Information Services (IIS)/ASP.NET environment.