.NET Framework

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Common Language Infrastructure (CLI)

Main article: Common Language Infrastructure

The purpose of the Common Language Infrastructure (CL) is to provide a language-neutral platform for application development and execution, including functions for Exception handling, Garbage Collection, security, and interoperability. By implementing the core aspects of the .NET Framework within the scope of the CL, this functionality will not be tied to a single language but will be available across the many languages supported by the framework. Microsoft's implementation of the CLI is called the Common Language Runtime, or CL.

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.NET Assembly

Assembly names

The name of an assembly consists of four parts

The short name. On Windows this is the name of the Portable Executable (PE) file without the extension.
The culture. This is an RFC 1766 identifier of the locale for the assembly. In general, library and process assemblies should be culture neutral; the culture should only be used for satellite assemblies.
The version. This is a dotted number made up of four values — major, minor, build and revision.
A public key token. This is a 64-bit hash of the public key that corresponds to the private key used to sign[1] the assembly. A signed assembly is said to have a strong name.

The public key token is used to make the assembly name unique. Thus, two strong named assemblies can have the same PE file name and yet .NET will recognize them as different assemblies. The Windows file system (FAT32 and NTFS) only recognizes the PE file name, so two assemblies with the same PE file name (but different culture, version or public key token) cannot exist in the same Windows folder. To solve this issue .NET introduces the GAC (Global Assembly Cache) that is treated as a single folder by the .NET CLR, but is actually implemented using nested file system folders.

To prevent spoofing attacks, where a cracker would try to pass off an assembly appearing as something else, the assembly is signed with a private key. The developer of the intended assembly keeps the private key secret, so a cracker cannot have access to it nor simply guess it. Thus the cracker cannot make his assembly impersonate something else, lacking the possibility to sign it correctly after the change. Signing the assembly involves taking a hash of important parts of the assembly and then encrypting the hash with the private key. The signed hash is stored in the assembly along with the public key. The public key will decrypt the signed hash. When the CLR loads a strongly named assembly it will generate a hash from the assembly and then compare this with the decrypted hash. If the comparison succeeds then it means that the public key in the file (and hence the public key token) is associated with the private key used to sign the assembly. This will mean that the public key in the assembly is the public key of the assembly publisher and hence a spoofing attack is prevented.

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.Net Framework For Developer

The .NET Framework provides the following services for application developers:

Memory management. In many programming languages, programmers are responsible for allocating and releasing memory and for handling object lifetimes. In .NET Framework applications, the CLR provides these services on behalf of the application.

A common type system. In traditional programming languages, basic types are defined by the compiler, which complicates cross-language interoperability. In the .NET Framework, basic types are defined by the .NET Framework type system and are common to all languages that target the .NET Framework.

An extensive class library. Instead of having to write vast amounts of code to handle common low-level programming operations, programmers can use a readily accessible library of types and their members from the .NET Framework Class Library.

Development frameworks and technologies. The .NET Framework includes libraries for specific areas of application development, such as ASP.NET for web applications, ADO.NET for data access, and Windows Communication Foundation for service-oriented applications.

Language interoperability. Language compilers that target the .NET Framework emit an intermediate code named Common Intermediate Language (CIL), which, in turn, is compiled at run time by the common language runtime. With this feature, routines written in one language are accessible to other languages, and programmers can focus on creating applications in their preferred language or languages.

Version compatibility. With rare exceptions, applications that are developed by using a particular version of the .NET Framework can run without modification on a later version.

Side-by-side execution. The .NET Framework helps resolve version conflicts by allowing multiple versions of the common language runtime to exist on the same computer. This means that multiple versions of applications can also coexist, and that an application can run on the version of the .NET Framework with which it was built.

Multitargeting. By targeting the .NET Framework Portable Class Library, developers can create assemblies that work on multiple .NET Framework platforms, such as the .NET Framework, Silverlight, Windows Phone 7, or Xbox 360.

You can choose any programming language that supports the .NET Framework to create your application. Because the .NET Framework provides language independence and interoperability, you can interact with other .NET Framework applications and components regardless of the language with which they were developed.

To develop .NET Framework applications or components