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.NET Framework

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.NET Framework
Developer(s)Microsoft
Stable release
Operating systemWindows 98 and above
TypeSystem platform
LicenseProprietary software
Websitewww.microsoft.com/net/

The Microsoft .NET Framework is a component of the Microsoft Windows operating system. It provides a large body of pre-coded solutions to common program requirements, and manages the execution of programs written specifically for the framework. The .NET Framework is a key Microsoft offering, and is intended to be used by most new applications created for the Windows platform.

The pre-coded solutions form the framework's class library and cover a large range of programming needs in areas including the user interface, data access, cryptography, numeric algorithms, and network communications. The functions of the class library are used by programmers who combine them with their own code to produce applications.

Programs written for the .NET framework execute in a software environment that manages the program's runtime requirements. This runtime environment, which is also a part of the .NET framework, is known as the Common Language Runtime (CLR). The CLR provides the appearance of an application virtual machine, so that programmers need not consider the capabilities of the specific CPU that will execute the program. The CLR also provides other important services such as security guarantees, memory management, and exception handling.

The class library and the CLR together comprise the .NET framework. The framework is intended to make it easier to develop computer applications and to reduce the vulnerability of applications and computers to security threats. First released in 2002, it is included with current versions of Microsoft Windows, and can be installed on most older versions. The current version is 2.0, which was released in November 2005 in conjunction with Visual Studio 2005.

Significance

For software developers, the .NET framework is one of the most significant changes to the Windows platform since its introduction. It brings into the operating system features and responsibilities that previously had been provided individually by programming languages and tools from various sources. The incorporation of the features into the OS offers a number of advantages, including:

  • Assuring the availability of framework features to all programs written in any of the .NET languages.
  • Providing to programmers a common means of accessing framework features, regardless of programming language.
  • Guarantees of a common behavior within the framework, regardless of programming language.
  • Allowing the operating system to provide some guarantees of program behavior, especially with respect to security, that it otherwise could not offer.
  • Reducing the complexity and limitations of program-to-program communication, even when those programs are written in different .NET languages.

These qualities are examined in more detail later in this article.

Rationale

The creation of the .NET framework reflects what has been learned over the years about the typical challenges that programmers face and useful approaches to those challenges.

Individual programming languages and tools led the way in proving the viability of features such as strong data typing, garbage-collected memory management, exception-based error handling, virtual machine architectures, and comprehensive class libraries. Visual Basic, Powerbuilder, the C++ Standard Template Library (STL), and other languages each implemented at least some of these features, but the Java language and its framework J2SE became the most notable success. Its popularity positioned it as a competitive threat to Microsoft. After failed attempts (due to copyright issues) to include a modified form of Java with Windows, Microsoft set out to create its own products that incorporated the best features of that and other languages. The effort resulted in the Microsoft .NET framework and its accompanying programming languages and tools.

Design goals and principal features

The .NET Framework was designed with several intentions:

  • Interoperability - Because so many COM libraries have already been created, the .NET Framework provides methods for allowing interoperability between new code and existing libraries.
  • Common Runtime Engine - Programming languages on the .NET Framework compile into an intermediate language known as the Common Intermediate Language, or CIL; Microsoft's implementation of CIL is known as Microsoft Intermediate Language, or MSIL. In Microsoft's implementation, this intermediate language is not interpreted, but rather compiled in a manner known as just-in-time compilation (JIT) into native code. The combination of these concepts is called the Common Language Infrastructure (CLI), a specification; Microsoft's implementation of the CLI is known as the Common Language Runtime (CLR).
  • Language Independence - The .NET Framework introduces a Common Type System, or CTS. The CTS specification defines all possible datatypes and programming constructs supported by the CLR and how they may or may not interact with each other. Because of this feature, the .NET Framework supports development in multiple programming languages. This is discussed in more detail in the .NET languages section below.
  • Base Class Library - The Base Class Library (BCL), sometimes referred to as the Framework Class Library (FCL), is a library of types available to all languages using the .NET Framework. The BCL provides classes which encapsulate a number of common functions such as file reading and writing, graphic rendering, database interaction, XML document manipulation, and so forth.
  • Simplified Deployment - Installation and deployment of Windows applications has been the bane of many developers' existence. Registry settings, file distribution and DLL hell have been nearly completely eliminated by new deployment mechanisms in the .NET Framework.
  • Security - .NET allows for code to be run with different trust levels without the use of a separate sandbox.

The design of the .NET framework is such that it supports platform independence. That is, a program written to use the framework should run without change on any type of computer for which the framework is implemented. At present, Microsoft has implemented the full framework only on the Windows operating system. Microsoft and others have implemented portions of the framework on non-Windows systems, but to date those implementations are not widely used.

.NET Framework architecture

Visual overview of the Common Language Infrastructure (CLI)

Common Language Infrastructure (CLI)

Main article: Common Language Infrastructure

The most important component of the .NET Framework lies in the Common Language Infrastructure, or CLI. The purpose of the CLI is to provide a language agnostic platform for application development, including, but not limited to, components for: exception handling, garbage collection, security, and interoperability. Microsoft's implementation of the CLI is called the Common Language Runtime, or CLR. The CLI is composed of five primary parts:

Assemblies

Main article: .NET assembly

The intermediate MSIL code is housed in .NET assemblies, which for the Windows implementation means a Portable Executable (PE) file or DLL. Assemblies are the .NET unit of deployment, versioning and security. The assembly can be made up of one or more files, but one of these must contain the manifest, which has the metadata for the assembly. The complete name of an assembly contains its simple text name, version number, culture and public key token; it must contain the name, but the others are optional. The public key token is generated when the assembly is created, and is a value that uniquely represents the name and contents of all the assembly files, and a private key known only to the creator of the assembly. Two assemblies with the same public key token are guaranteed to be identical. If an assembly is tampered with (for example, by hackers), the public key can be used to detect the tampering.

Metadata

Main article: .NET metadata

All CIL is self-describing through .NET metadata. The CLR checks on metadata to ensure that the correct method is called. Metadata is usually generated by language compilers but developers can create their own metadata through custom attributes.

Base Class Library (BCL)

Main article: Base Class Library

The Base Class Library (BCL), sometimes referred to as the Framework Class Library (FCL), is a library of types available to all languages using the .NET Framework. The BCL provides classes which encapsulate a number of common functions such as file reading and writing, graphic rendering, database interaction, XML document manipulation, and so forth. The BCL is much larger than other libraries, but has much more functionality in one package.

Security

.NET has its own security mechanism, with two general features: Code Access Security (CAS), and validation and verification. Code Access Security is based on evidence that is associated with a specific assembly. Typically the evidence is the source of the assembly (whether it is installed on the local machine, or has been downloaded from the intranet or Internet). Code Access Security uses evidence to determine the permissions granted to the code. Other code can demand that calling code is granted a specified permission. The demand causes the CLR to perform a call stack walk: every assembly of each method in the call stack is checked for the required permission and if any assembly is not granted the permission then a security exception is thrown.

When an assembly is loaded the CLR performs various tests. Two such tests are validation and verification. During validation the CLR checks that the assembly contains valid metadata and CIL, and it checks that the internal tables are correct. Verification is not so exact. The verification mechanism checks to see if the code does anything that is 'unsafe'. The algorithm used is quite conservative and hence sometimes code that is 'safe' is not verified. Unsafe code will only be executed if the assembly has the 'skip verification' permission, which generally means code that is installed on the local machine.

Standardization and Licensing

In August, 2000, Microsoft, Hewlett-Packard, and Intel worked to standardize CLI and the C# programming language. By December, 2001, both were ratified ECMA standards (ECMA 335 and ECMA 334). ISO followed in April, 2003 (ISO/IEC 23271 and ISO/IEC 23270).

While Microsoft and their partners hold patents for CLI and C#, ECMA and ISO requires that all patents essential to implementation be made available under "reasonable and non-discriminatory (RAND) terms." The companies have agreed to make the patents available under "royalty-free and otherwise RAND terms."

Versions

Since it was first released in 2002, Microsoft has provided two minor upgrades and one major upgrade, interspersed with several maintenance releases (known as Service Packs).

.NET Framework 1.0

Full version number - 1.0.3705

This is the initial .NET Framework, released in January 2002. It is available on its own as a redistributable package or in a software development kit. It is also part of the first release of Microsoft Visual Studio .NET (also known as Visual Studio .NET 2002).

  • .NET Framework 1.0 RTM 1.0.3705.0
  • .NET Framework 1.0 Sp1 1.0.3705.209
  • .NET Framework 1.0 Sp2 1.0.3705.288
  • .NET Framework 1.0 Sp3 1.0.3705.6018

.NET Framework 1.1

Full version number - 1.1.4322

This is the first major .NET Framework upgrade, released in April 2003. It is available on its own as a redistributable package or in a software development kit. 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 - it is part of Windows Server 2003.

  • .NET Framework 1.1 RTM 1.1.4322.573
  • .NET Framework 1.1 Sp1 1.1.4322.2032
  • Windows 2003 RTM 1.1.4322.573
  • Windows 2003 Service Pack 1 1.1.4322.2300

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. For a detailed list, see GotDotNet: API Changes between versions of the .NET Framework.

.NET Framework 2.0

Full version number - 2.0.50727.42 Released on November 7, 2005, along with Visual Studio 2005, SQL 2005 and BizTalk 2006.

Changes since 1.1

  • Numerous API changes. For a detailed list, see GotDotNet: API Changes between versions of the .NET Framework.
  • 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

.NET Framework 3.0

Template:Beta software

File:DotNet3.0.png
Architecture of the .NET Framework 3.0

.NET Framework 3.0, formerly called WinFX[1], includes a new set of managed code APIs that are an integral part of the upcoming Windows Vista and Windows Server "Longhorn" operating systems. It will also be available for Windows XP SP2 and Windows Server 2003. There are no major architectural changes being included with this release; .NET Framework 3.0 includes version 2.0 of the Common Language Runtime.

.NET Framework 3.0 consists of four major components:

Microsoft released a Community Technology Preview of .NET Framework 3.0 on June 23 2006[2] for Windows XP. The same version of the Framework is installed by default in Windows Vista build 5456, released to beta testers at around the same time.

.NET Framework 3.5

Template:Future software In an interview with Channel9, Jason Zander, general manager of the .NET Framework team at Microsoft, discussed the version of the framework that will follow version 3.0.[3] Tentatively titled "version 3.5", this version will include a new compiler that will support new features such as Language Integrated Query, as well as new language features in C# and VB.NET. This version of the framework is slated to be included with the version of Visual Studio following the 2005 release.

.NET vs. Java EE

The CLI, the CIL, and C# have similarities to Sun's JVM and Java; hence, they are fierce competitors. Both use their own intermediate byte-code, Microsoft calling theirs Microsoft Intermediate Language (MSIL). MSIL is designed for just-in-time compilation (JITting), while Java bytecode is generally designed to be interpreted, not JITted (However Sun's HotSpot is a successful JIT implementation of Java). .NET is currently only fully available on Windows platforms, whereas Java is fully available on many platforms. However, Microsoft did release source code for portions of the .NET framework, including the C++ source code for some of their CLR. This forms the basis of the Shared source CLI. It along with other implementations currently in progress such as Portable.NET and Mono can be used to run some .NET applications on Unix-like operating systems such as Linux, FreeBSD, and Mac OS X. Java EE is an alternative, providing different functionality than the .NET framework and other Microsoft technologies such as COM+ (previously MTS) and MSMQ.

More cooperation is possible with the software "IKVM", which is an implementation of the Java Virtual Machine in .NET.

Java has an alternative implementation of remote procedure calls and network transparency called remote method invocation (RMI). RMI in its "RMI over IIOP" (RMI-IIOP) variant is also compatible with CORBA.

It is important to distinguish between the .NET Platform, and the individual languages (C# and VB.NET) used to develop for the platform. Similarly, the Java platform is distinct from the actual Java language, as other source languages can be compiled down to Java Byte Code. With this warning in mind, it may be useful to read a comparison of Java and C#.

Criticism

Some concerns and criticisms relating to the .NET Framework include:

  • The introduction of the .NET Framework has resulted in many changes to Microsoft development tools and languages. Some of these changes are controversial, especially for developers transitioning from an earlier version of a Microsoft product.[4]
  • Applications running in a managed environment such as the Microsoft framework's CLR or Java's JVM tend to require more system resources than functionally similar applications that access machine resources more directly. In general, applications that require maximum performance or precise timing of operations would be written in C, unmanaged C++, or other languages that emphasize performance.

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 a ECMA/ISO specification, other implementations of it are unencumbered by copyright 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 shared source implementation of the CLR component of the .NET Framework. It runs on Microsoft Windows XP, FreeBSD, and Mac OS X 10.2.
  • Portable.NET 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.
  • 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.

See also

References

  1. ^ WinFX name change announcement
  2. ^ http://www.microsoft.com/downloads/details.aspx?FamilyID=8D09697E-4868-4D8D-A4CF-9B82A2AE542D&displaylang=en
  3. ^ Jason Zander on the WinFX to .NET FX 3.0 rename
  4. ^ Controversy transitioning from VB to VB.NET

Microsoft

  • ".NET Framework Developer Center". Microsoft Developer Network. Retrieved 2006-07-18.
  • "Windows Vista". Microsoft Developer Network. Retrieved 2006-07-18.
  • "GotDotNet". Microsoft Developer Network. Retrieved 2006-07-18.

Other

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