| 摘要 |
A set of attached extensions is reduced before it is exposed to the code of a processing extension point to which the extensions are attached. An application calls an extension registry to obtain a list of available extensions attached to a given extension point, and filter functionality is integrated into the extension registry. Filters including filtering logic are plugged into the extension registry itself, and the extension registry selects the filter or filters to be applied for a current context. The extension registry itself defines an extension point to collect filters as extensions and to define an interface that those filters will implement. Each filter specifies when it should be called. As a result, an application can supply a filter that knows what extensions to expose and which to exclude in one or more contexts, and provide a hint to the extension registry indicating when the extension registry should apply the filter. Each filter can specify a name of an extension registry instance, allowing the application to specify that name when obtaining an extension registry instance. The named instance of the extension registry can then search for filters that specify its name, when the application requests extensions for a given extension point.
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