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Global Assembly Cache

Definition

The Global Assembly Cache (GAC) is a machine-wide cache of code libraries for Microsoft’s .NET framework. It stores .NET assemblies that are specifically designated to be shared by all applications executed on a system. The GAC helps resolve and manage the shared dependencies of these applications, ensuring consistency and eliminating versioning conflicts.

Phonetic

The phonetics of the keyword “Global Assembly Cache” are:Global: /ˈɡloʊ.bəl/Assembly: /əˈsɛmbli/Cache: /kæʃ/

Key Takeaways

  1. Global Assembly Cache (GAC) is a machine-wide code cache provided by .NET Framework that can store shared .NET assemblies. These assemblies are universally accessible to all .NET applications on the machine. This eliminates the need to place duplicate copies of assemblies in every application.
  2. The GAC helps in managing the version policy where different versions of the same assembly can exist on the same machine. It supports running multiple versions of a component side by side, also known as side-by-side execution. It ensures that applications use the correct version of an assembly, thus addressing assembly versioning and resolving issues.
  3. An assembly must be strongly named, i.e., it must have a public key token, version number and culture information, to be eligible to be added into GAC. Strongly naming an assembly provides a unique identity and ensures its integrity. GAC provides benefit of security by supporting code signing to confirm the identity of the assembly’s author and to protect the assembly from modification after its creation.

Importance

The Global Assembly Cache (GAC) is a significant concept in .NET technology, primarily due to the role it plays in managing shared assemblies. It essentially serves as a repository for shared assemblies in .NET, promoting better versioning and eliminating DLL Hell, a situation that arises when multiple applications attempt to use a common DLL, causing conflicts and malfunctions. The GAC empowers .NET to effectively manage different versions of DLLs, maintain strong names for assemblies, and optimally share DLLs among numerous applications. The central control it provides enhances the overall system’s stability and the reusability of codes, making it a vital component in .NET technology.

Explanation

The Global Assembly Cache, commonly abbreviated as GAC, is an essential component within Microsoft’s .NET Framework. Its main purpose is to provide a centralized location for storing and sharing .NET assemblies. These assemblies, which are libraries of compiled code, can be securely installed and accessible to all .NET applications, serving as a form of shared library concept. The GAC helps to solve versioning problems as well as code redundancy, as it allows applications on a given system to share assemblies instead of having to load a local copy of the same assembly.The use of the Global Assembly Cache plays a crucial role in resolving assembly versions upon runtime. It facilitates version policy, ensuring that if multiple versions of the same assembly exist, the correct one gets used according to the version policy. This minimizes potential conflicts and errors resulting from diverse application requirements. Furthermore, GAC provides security benefits; any assemblies installed into the GAC must have a strong name, which guarantees the uniqueness of the assembly and ensures its origin and integrity, making its deployment safer. Overall, GAC is an integral tool in managing, sharing, and controlling versions of assemblies within the .NET environment.

Examples

1. Microsoft .NET Framework: Global Assembly Cache (GAC) is a machine-wide cache of assemblies that are used by .NET applications. This framework is the most common example of GAC as it allows developers to share and run applications across different .NET programs.2. Microsoft SharePoint: In Microsoft SharePoint, any custom solution requiring a shared resource or to be used commonly across multiple applications, are installed into the GAC. This allows multiple programs to use the same version of an assembly in a more secure and efficient way, thereby enhancing the overall system performance.3. Enterprise-Level Software: For large organizations running enterprise-level software such as ERP or CRM systems, shared assemblies that are often critical for system functionality are used. These shared resources are installed in the GAC, enabling multiple applications to access the same assembly from one consolidated, centralized cache.

Frequently Asked Questions(FAQ)

Q: What is the Global Assembly Cache (GAC)?A: The Global Assembly Cache (GAC) is a machine-wide CLI assembly cache for the Common Language Infrastructure (CLI) in Microsoft’s .NET Framework. It stores .NET assemblies that are specifically designated to be shared by numerous applications on the computer.Q: Why do we use the Global Assembly Cache?A: We use the GAC to share .NET assemblies across multiple applications. It helps in avoiding DLL Hell and versioning problems. Moreover, it provides the benefit of maintaining strong naming of shared assemblies.Q: How can I view the contents of the GAC?A: To view the contents of the GAC, browse to the %windir%\assembly folder in Windows Explorer, where %windir% is your Windows directory. Q: How do I install an assembly into the GAC?A: There are several ways to install an assembly into the GAC, the most common being the use of the gacutil tool included with Visual Studio or manually copying the file into the Assembly folder in Windows.Q: Can any assembly be installed in the GAC?A: No, only assemblies that have a strong name can be installed in the GAC. A strong name includes the assembly’s identity – its text name, version number, and culture information (if provided) – plus a public key and a digital signature.Q: What color coding means in GAC?A: The GAC uses different color coding for assemblies in the %windir%\Assembly folder to differentiate between Global, Native Images, and Downloaded assemblies. Q: Is the GAC necessary for all .NET applications?A: No, the GAC is not necessary for all .NET applications. It’s primarily used for shared assemblies, and most desktop applications will work perfectly well with application-private assemblies. Q: What is gacutil.exe in the context of GAC?A: gacutil.exe is a tool provided by Microsoft that can be used to manage the contents of the GAC. It allows for the installation, removal, and viewing of the assemblies within the cache.Q: How is versioning handled in the GAC?A: The GAC allows multiple versions of the same assembly to coexist. This helps manage versioning as applications can specify exactly which version of an assembly they need to function.

Related Tech Terms

  • .NET Framework
  • Assembly manifest
  • Shared assemblies
  • Strong-named assemblies
  • Assembly versioning

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