/// <summary>
/// Gets a value indicating whether the image is new or updated in an asynchronous manner.
/// </summary>
/// <returns>
/// The <see cref="Task"/>.
/// </returns>
public override async Task <bool> IsNewOrUpdatedAsync()
{
// TODO: Before this check is performed it should be throttled. For example, only perform this check
// if the last time it was checked is greater than 5 seconds. This would be much better for perf
// if there is a high throughput of image requests.
string cachedFileName = await this.CreateCachedFileNameAsync().ConfigureAwait(false);
this.CachedPath = CachedImageHelper.GetCachedPath(this.absoluteCachePath, cachedFileName, false, this.FolderDepth);
this.virtualCachedFilePath = CachedImageHelper.GetCachedPath(this.virtualCachePath, cachedFileName, true, this.FolderDepth);
bool isUpdated = false;
CachedImage cachedImage = CacheIndexer.Get(this.CachedPath);
if (cachedImage == null)
{
var info = new FileInfo(this.CachedPath);
if (info.Exists)
{
cachedImage = new CachedImage
{
Key = Path.GetFileNameWithoutExtension(this.CachedPath),
Path = this.CachedPath,
CreationTimeUtc = info.LastWriteTimeUtc
};
CacheIndexer.Add(cachedImage, this.ImageCacheMaxMinutes);
}
}
if (cachedImage == null)
{
// Nothing in the cache so we should return true.
isUpdated = true;
}
else
{
// Check to see if the cached image is set to expire
// or a new file with the same name has replaced our current image
if (this.IsExpired(cachedImage.CreationTimeUtc) || await this.IsUpdatedAsync(cachedImage.CreationTimeUtc).ConfigureAwait(false))
{
CacheIndexer.Remove(this.CachedPath);
isUpdated = true;
}
else
{
// Set cachedImageCreationTimeUtc so we can sender Last-Modified or ETag header when using Response.TransmitFile()
this.cachedImageCreationTimeUtc = cachedImage.CreationTimeUtc;
}
}
return(isUpdated);
}
/// <summary>
/// Gets a string identifying the cached file name.
/// </summary>
/// <returns>
/// The asynchronous <see cref="Task"/> returning the value.
/// </returns>
public virtual async Task <string> CreateCachedFileNameAsync()
{
return(await Task.FromResult(CachedImageHelper.GetCachedImageFileName(this.FullPath, this.Querystring)));
}
/// <summary> /// Gets a string identifying the cached file name. /// </summary> /// <returns> /// The asynchronous <see cref="Task"/> returning the value. /// </returns> public virtual Task <string> CreateCachedFileNameAsync() => Task.FromResult(CachedImageHelper.GetCachedImageFileName(this.FullPath, this.Querystring));
