.NET Framework Conceptual Overview

The .NET Framework is an integral Windows component that supports building and running the next generation of applications and XML Web services. The .NET Framework is designed to fulfill the following objectives:
To provide a consistent object-oriented programming environment whether object code is stored and executed locally, executed locally but Internet-distributed, or executed remotely.
To provide a code-execution environment that minimizes software deployment and versioning conflicts.
To provide a code-execution environment that promotes safe execution of code, including code created by an unknown or semi-trusted third party.
To provide a code-execution environment that eliminates the performance problems of scripted or interpreted environments.
To make the developer experience consistent across widely varying types of applications, such as Windows-based applications and Web-based applications.
To build all communication on industry standards to ensure that code based on the .NET Framework can integrate with any other code.
The .NET Framework has two main components: the common language runtime and the .NET Framework class library. The common language runtime is the foundation of the .NET Framework. You can think of the runtime as an agent that manages code at execution time, providing core services such as memory management, thread management, and remoting, while also enforcing strict type safety and other forms of code accuracy that promote security and robustness. In fact, the concept of code management is a fundamental principle of the runtime. Code that targets the runtime is known as managed code, while code that does not target the runtime is known as unmanaged code. The class library, the other main component of the .NET Framework, is a comprehensive, object-oriented collection of reusable types that you can use to develop applications ranging from traditional command-line or graphical user interface (GUI) applications to applications based on the latest innovations provided by ASP.NET, such as Web Forms and XML Web services.
The .NET Framework can be hosted by unmanaged components that load the common language runtime into their processes and initiate the execution of managed code, thereby creating a software environment that can exploit both managed and unmanaged features. The .NET Framework not only provides several runtime hosts, but also supports the development of third-party runtime hosts.
For example, ASP.NET hosts the runtime to provide a scalable, server-side environment for managed code. ASP.NET works directly with the runtime to enable ASP.NET applications and XML Web services, both of which are discussed later in this topic.
Internet Explorer is an example of an unmanaged application that hosts the runtime (in the form of a MIME type extension). Using Internet Explorer to host the runtime enables you to embed managed components or Windows Forms controls in HTML documents. Hosting the runtime in this way makes managed mobile code (similar to Microsoft® ActiveX® controls) possible, but with significant improvements that only managed code can offer, such as semi-trusted execution and isolated file storage.

Beginner to .NET

Dotnet Lore shares about .net Technology from Beginner to Expert level Day by day .
NET (dot-net) is the name Microsoft gives to its general vision of the future of computing, the view being of a world in which many applications run in a distributed manner across the Internet. We can identify a number of different motivations driving this vision.
Firstly, distributed computing is rather like object oriented programming, in that it encourages specialised code to be collected in one place, rather than copied redundantly in lots of places. There are thus potential efficiency gains to be made in moving to the distributed model.
Secondly, by collecting specialised code in one place and opening up a generally accessible interface to it, different types of machines (phones, handhelds, desktops, etc.) can all be supported with the same code. Hence Microsoft's 'run-anywhere' aspiration.
Thirdly, by controlling real-time access to some of the distributed nodes (especially those concerning authentication), companies like Microsoft can control more easily the running of its applications. It moves applications further into the area of 'services provided' rather than 'objects owned'.
Interestingly, in taking on the .NET vision, Microsoft seems to have given up some of its proprietary tendencies (whereby all the technology it touched was warped towards its Windows operating system). Because it sees its future as providing software services in distributed applications, the .NET framework has been written so that applications on other platforms will be able to access these services. For example, .NET has been built upon open standard technologies like XML and SOAP.
At the development end of the .NET vision is the .NET Framework. This contains the Common Language Runtime, the .NET Framework Classes, and higher-level features like ASP.NET (the next generation of Active Server Pages technologies) and WinForms (for developing desktop applications).
The Common Language Runtime (CLR) manages the execution of code compiled for the .NET platform. The CLR has two interesting features. Firstly, its specification has been opened up so that it can be ported to non-Windows platforms. Secondly, any number of different languages can be used to manipulate the .NET framework classes, and the CLR will support them. This has led one commentator to claim that under .NET the language one uses is a 'lifestyle choice'.
Not all of the supported languages fit entirely neatly into the .NET framework, however (in some cases the fit has been somewhat Procrustean). But the one language that is guaranteed to fit in perfectly is C#. This new language, a successor to C++, has been released in conjunction with the .NET framework, and is likely to be the language of choice for many developers working on .NET applications.