程序集： Microsoft.ApplicationServer.Caching.Core（在 Microsoft.ApplicationServer.Caching.Core.dll 中）
For objects stored in regions, the Key is only unique relative to other objects in that particular region. For objects not stored in regions, the Key is only unique relative to other objects not stored in regions in the same cache. The same Key can exist more than once in a cache if the additional keys are stored within different regions.
The DataCacheItem class is especially useful for updating tags associated with the object and concurrency operations. Tags are not supported in Windows Azure Shared Caching.