# AppFabric Caching

AppFabric Caching provides an in-memory, distributed cache platform for Windows Server. Microsoft developed AppFabric Caching and released it as part of AppFabric.

## Architecture

AppFabric Caching stores serialized managed objects in a cache cluster. The cache cluster consists of one or more machines that pool their available physical memory. This pooled memory is presented to cache clients as a single source of caching memory. Objects are stored and accessed using an associated key value.
AppFabric Caching features must be installed on each server in the cache cluster. Following installation, the AppFabric Configuration Wizard must be used to join each server to the cache cluster. An external file share or database is required to maintain the cache cluster configuration settings. A set of Windows PowerShell commands for Caching provides administration capabilities on the cache cluster.

## Code examples

Note that the code samples in this section are shown in C#.
A common task is to create code that puts, retrieves, and removes objects from the cache. These operations target either the default cache or a named cache.
First, create a static DataCache member:
Next, create a method that accesses this cache. The properties of the cache can be stored in the app.config or web.config files. The cache settings can also be programmatically configured. The following example shows how to programmatically configure the cache.
The following method shows how to use the _cache object to retrieve data from the cache. In this example, a user identifier (userId) is the key for the associated user information object. The code first attempts to get this user information from the cache using the userId key. If that does not succeed, the code retrieves the information with a database query and then stores the returned user data in the cache. The next time the same code is run, the user information will be returned from the cache rather than the database. This assumes that the cached data has not been expired or evicted.
The following method shows how to update data that is already in the cache.
The following call removes the item from the cache.

## History

Originally, AppFabric Caching had several beta releases under the code name Velocity. In June 2010, Microsoft officially released AppFabric Caching as part of AppFabric. For more detailed information, see the history section of the AppFabric page.

## Related caching technologies

AppFabric Caching is related to other Microsoft caching technologies. These technologies share similar features, such as the assembly name, namespace, and types. However, there are some differences. The table below describes these technologies.
| Caching Technology | Target | Installed By | Description |
| AppFabric Caching | On-premises | AppFabric | Distributed on-premises cache that uses servers that the user provisions and manages. |
| Windows Azure Caching | Cloud | Windows Azure SDK | Caching is distributed across the instances of a single role in a Windows Azure cloud service deployment. |
| Windows Azure Shared Caching | Cloud | Windows Azure SDK | Caching is provided as a multitenant service for use by Windows Azure cloud services. |