ASP.NET Output Cache with Custom Hooks
Using the NCache output provider, the output of pages and controls is stored in the cache. In some scenarios, it can be very helpful if the page/control output can be grouped according to some criteria before insertion into the cache. Here to provide the end user with further control, NCache provides a concept of “hooks”. Hooks allow users to group the output of pages/controls before its insertion into the cache.
The following configuration changes are required:
Prerequisites
- Install the following NuGet packages in your application based on your NCache version:
- Enterprise: AspNet.OutputCache.NCache
- Professional: AspNet.OutputCache.NCache.Professional
- To utilize the extension, include the following namespaces in your application in Startup.cs:
- The cache must be running.
- For API details, refer to: NOutputCacheProvider.
- Make sure that the data being added is serializable.
- To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.
- To handle any unseen exceptions, refer to the Troubleshooting section.
Modify Web.Config
<!-- caching section group -->
<caching>
<outputCache defaultProvider="NOutputCacheProvider">
<providers>
<add name="NOutputCacheProvider"
type="Alachisoft.NCache.OutputCacheProvider.NOutputCacheProvider, Alachisoft.NCache.OutputCacheProvider, Version=x.x.x.x, Culture=neutral, PublicKeyToken=cff5926ed6a5376"
exceptionsEnabled="false"
enableLogs="true"
cacheName="demoClusteredCache"
writeExceptionsToEventLog="false"
hookAssemblyName="OutputCache, Version=x.x.x.x, Culture=neutral, PublicKeyToken=null" hookClassName="Sample.OutputCacheProvider.OutputCacheHook.OutputCacheHookSample"/>
</providers>
</outputCache>
</caching>
Note
Replace Version=x.x.x.x with the actual NCache version that you have installed.
Sample Implementation of IOutputCacheHook
class OutputCache : IOutputCacheHook
{
public void Initialize()
{
// initialize required elements here, according to business logic.
}
public CacheMetadata OnCachingOutput(HttpContext context, string key, object value, CacheOperation operation, ref DateTime utcExpiry)
{
CacheMetadata cacheMetaData = null;
if (context != null)
{
cacheMetaData = new CacheMetadata();
// Put required business logic to categorize input parameter key in desired group
// Groups, sub groups, tags, named tags and dependencies can be assigned
// to object of cacheMetaData which is returned to be inserted into cache
cacheMetaData.GroupName = "vendorState";
cacheMetaData.Dependency = new KeyDependency(key);
utcExpiry = DateTime.Now.AddMinutes(5);
}
return cacheMetaData;
}
public void Dispose()
{
// Dispose the initialized elements here
}
}
Configuration Members
Output Cache with custom hooks allows grouping of data before storing it into the cache. To implement IOutputCacheHook
, create a class that extends IOutputCacheHook
. The following tables list the properties and methods that must be implemented.
Methods | Description |
---|---|
Initialize |
Initializes required elements of OutputCacheHook . |
OnCachingOutput |
Takes as input the HttpContext instance for the current request, string key and object value generated by the framework for output is passed as is an input parameter. Input parameter CacheOperation type can be added or set, concerning the OutputCache Provider operations of Add and Set . DateTime utcExpiry is passed as a reference parameter which allows end-user code to reset expiration for a particular key-value pair. If the value for expiration is not set, the default value provided by the framework is used. This method returns CacheMetadata that can have additional information about the group, subgroup, tag, named tag, and dependency settings. This method functions as a hook between the OutputCache Provider and user code. It is called when output is generated by the framework but before insertion into the cache. Thus, allowing an intermediate hook for a user, where additional information can be added with CacheMetadata . |
Dispose |
It releases resources that are no longer in use by OutputCacheHook . |
See Also
.NET: Alachisoft.NCache.OutputCacheProvider namespace.