/// <summary>
/// Inserts a new cache decorator at the start of the chain of decorators terminating at the
/// <paramref name="decorated"/> instance supplied
/// </summary>
/// <param name="decorated">The existing cache to insert a new cache decorator into it's chain</param>
/// <param name="createDecoration">
/// A delegate that takes the cache at the head of the chain and creates the decorator to be inserted
/// </param>
public virtual ICache InsertDecoratorAtStartOfChain(ICache decorated,
Func <ICache, CacheDecorator> createDecoration)
{
var cacheDecorator = (CacheDecorator)decorated.GetDecoratorChain().LastOrDefault();
if (cacheDecorator == null)
{
return(createDecoration(decorated));
}
// we need to insert statistics decorator as the first decorator in the chain
// this means redefining the existing chain...
// the reason why we need to do this is a decorator at the end of the chain can be by-passed using the
// ICache.As method.
// By adding the statistics cache at the start of the chain we ensure that it will always be called
// find the last decorator in the chain
CacheDecorator insert = createDecoration(cacheDecorator.DecoratedCache);
cacheDecorator.DecoratedCache = insert;
return(decorated);
}
public virtual ICache InsertDecoratorBetween <TStart, TEnd>(ICache decorated,
Func <ICache, CacheDecorator> createDecoration)
where TEnd : class, ICache where TStart : class, ICache
{
List <CacheDecorator> chain = decorated.GetDecoratorChain().OfType <CacheDecorator>().ToList();
var end = chain.CacheOfType <TEnd>().LastOrDefault() as CacheDecorator;
var start = chain.CacheOfType <TStart>().LastOrDefault() as CacheDecorator;
if (!ReferenceEquals(end, null))
{
int endPosition = chain.IndexOf(end);
if (endPosition == 0)
{
// create a new head for the existing chain
return(createDecoration(end));
}
else
{
// insert new decorator into exising chain
CacheDecorator insert = createDecoration(end);
CacheDecorator beforeEnd = chain[endPosition - 1];
beforeEnd.DecoratedCache = insert;
return(decorated);
}
}
else if (!ReferenceEquals(start, null))
{
CacheDecorator insert = createDecoration(start.DecoratedCache);
start.DecoratedCache = insert;
return(decorated);
}
else
{
// create a chain with our new decorator
return(createDecoration(decorated));
}
}