/// <summary>
/// Gets a data from cache if possible, otherwise from original source then sets cache.
/// </summary>
/// <typeparam name="T">Targeted data type.</typeparam>
/// <param name="cache">Cache provider.</param>
/// <param name="cacheKey">Cache key.</param>
/// <param name="options">Cache options.</param>
/// <param name="getWithoutCacheDelegate">Delegate to retrieve data from the original source.</param>
/// <returns>The data.</returns>
internal static async Task <T> GetOrSetFromCache <T>(
this IDistributedCache cache,
string cacheKey,
DistributedCacheEntryOptions options,
Func <Task <T> > getWithoutCacheDelegate)
where T : class, new()
{
T datas = await cache.GetFromCache <T>(cacheKey).ConfigureAwait(false);
if (datas == null)
{
SemaphoreSlim semaphore = _semaphores.GetOrAdd(cacheKey, new SemaphoreSlim(1, 1));
await semaphore.WaitAsync().ConfigureAwait(false);
try
{
datas = await cache.GetFromCache <T>(cacheKey).ConfigureAwait(false);
if (datas == null)
{
datas = await getWithoutCacheDelegate().ConfigureAwait(false);
if (datas != null)
{
await cache.SetAsync(cacheKey, Serialize(datas), options).ConfigureAwait(false);
}
}
}
finally
{
semaphore.Release();
}
}
return(datas);
}