public async Task DisplayedAsync(ShapeDisplayContext context)
{
var cacheContext = context.ShapeMetadata.Cache();
// If the shape is not configured to be cached, continue as usual
if (cacheContext == null)
{
if (context.ChildContent == null)
{
context.ChildContent = HtmlString.Empty;
}
return;
}
// If we have got this far, then this shape is configured to be cached.
// We need to determine whether or not the ChildContent of this shape was retrieved from the cache by the DisplayingAsync method above, as opposed to generated by the View Engine.
// ChildContent will be generated by the View Engine if it was not available in the cache when we rendered the shape.
// In this instance, we need insert the ChildContent into the cache so that subsequent attempt to render this shape can take advantage of the cached content.
// If the ChildContent was retrieved form the cache, then the Cache Context will be present in the _cached collection (see the DisplayingAsync method in this class).
// So, if the cache context is not present in the _cached collection, we need to insert the ChildContent value into the cache:
if (!_cached.ContainsKey(cacheContext.CacheId) && context.ChildContent != null)
{
// The content is pre-encoded in the cache so we don't have to do it every time it's rendered
using (var sb = StringBuilderPool.GetInstance())
{
using (var sw = new StringWriter(sb.Builder))
{
context.ChildContent.WriteTo(sw, HtmlEncoder.Default);
await _dynamicCacheService.SetCachedValueAsync(cacheContext, sw.ToString());
await sw.FlushAsync();
}
}
}
}
public async Task DisplayedAsync(ShapeDisplayContext context)
{
var cacheContext = context.Shape.Metadata.Cache();
// If the shape is not configured to be cached, continue as usual
if (cacheContext == null)
{
if (context.ChildContent == null)
{
context.ChildContent = HtmlString.Empty;
}
return;
}
// If we have got this far, then this shape is configured to be cached.
// We need to determine whether or not the ChildContent of this shape was retrieved from the cache by the DisplayingAsync method above, as opposed to generated by the View Engine.
// ChildContent will be generated by the View Engine if it was not available in the cache when we rendered the shape.
// In this instance, we need insert the ChildContent into the cache so that subsequent attempt to render this shape can take advantage of the cached content.
// If the ChildContent was retrieved form the cache, then the Cache Context will be present in the _cached collection (see the DisplayingAsync method in this class).
// So, if the cache context is not present in the _cached collection, we need to insert the ChildContent value into the cache:
if (!_cached.ContainsKey(cacheContext.CacheId) && context.ChildContent != null)
{
// The content is pre-encoded in the cache so we don't have to do it every time it's rendered
using var sw = new ZStringWriter();
// 'ChildContent' may be a 'ViewBufferTextWriterContent' on which we can't
// call 'WriteTo()' twice, so here we update it with a new 'HtmlString()'.
context.ChildContent.WriteTo(sw, _htmlEncoder);
var contentHtmlString = new HtmlString(sw.ToString());
context.ChildContent = contentHtmlString;
await _dynamicCacheService.SetCachedValueAsync(cacheContext, contentHtmlString.Value);
}
}
public async Task <IHtmlContent> ProcessContentAsync(TagHelperOutput output, CacheContext cacheContext)
{
IHtmlContent content = null;
while (content == null)
{
Task <IHtmlContent> result;
// Is there any request already processing the value?
if (!_dynamicCacheTagHelperService.Workers.TryGetValue(CacheId, out result))
{
// There is a small race condition here between TryGetValue and TryAdd that might cause the
// content to be computed more than once. We don't care about this race as the probability of
// happening is very small and the impact is not critical.
var tcs = new TaskCompletionSource <IHtmlContent>();
_dynamicCacheTagHelperService.Workers.TryAdd(CacheId, tcs.Task);
try
{
var value = await _dynamicCacheService.GetCachedValueAsync(cacheContext);
if (value == null)
{
// The value is not cached, we need to render the tag helper output
var processedContent = await output.GetChildContentAsync();
var stringBuilder = new StringBuilder();
using (var writer = new StringWriter(stringBuilder))
{
processedContent.WriteTo(writer, HtmlEncoder);
}
var formattingContext = new DistributedCacheTagHelperFormattingContext
{
Html = new HtmlString(stringBuilder.ToString())
};
await _dynamicCacheService.SetCachedValueAsync(cacheContext, formattingContext.Html.ToString());
content = formattingContext.Html;
}
else
{
content = new HtmlString(value);
}
}
catch
{
content = null;
throw;
}
finally
{
// Remove the worker task before setting the result.
// If the result is null, other threads would potentially
// acquire it otherwise.
_dynamicCacheTagHelperService.Workers.TryRemove(CacheId, out result);
// Notify all other awaiters to render the content
tcs.TrySetResult(content);
}
}
else
{
content = await result;
}
}
return(content);
}
public async Task <IHtmlContent> ProcessContentAsync(TagHelperOutput output, CacheContext cacheContext)
{
IHtmlContent content = null;
while (content == null)
{
Task <IHtmlContent> result;
// Is there any request already processing the value?
if (!_dynamicCacheTagHelperService.Workers.TryGetValue(CacheId, out result))
{
// There is a small race condition here between TryGetValue and TryAdd that might cause the
// content to be computed more than once. We don't care about this race as the probability of
// happening is very small and the impact is not critical.
var tcs = new TaskCompletionSource <IHtmlContent>();
_dynamicCacheTagHelperService.Workers.TryAdd(CacheId, tcs.Task);
try
{
var value = await _dynamicCacheService.GetCachedValueAsync(cacheContext);
if (value == null)
{
// The value is not cached, we need to render the tag helper output
var processedContent = await output.GetChildContentAsync();
using (var sb = StringBuilderPool.GetInstance())
{
using (var writer = new StringWriter(sb.Builder))
{
// Write the start of a cache debug block.
if (_cacheOptions.DebugMode)
{
// No need to optimize this code as it will be used for debugging purpose.
writer.WriteLine();
writer.WriteLine($"<!-- CACHE BLOCK: {cacheContext.CacheId} ({Guid.NewGuid()})");
writer.WriteLine($" VARY BY: {String.Join(", ", cacheContext.Contexts)}");
writer.WriteLine($" DEPENDENCIES: {String.Join(", ", cacheContext.Tags)}");
writer.WriteLine($" EXPIRES ON: {cacheContext.ExpiresOn}");
writer.WriteLine($" EXPIRES AFTER: {cacheContext.ExpiresAfter}");
writer.WriteLine($" EXPIRES SLIDING: {cacheContext.ExpiresSliding}");
writer.WriteLine("-->");
}
// Always write the content regardless of debug mode.
processedContent.WriteTo(writer, HtmlEncoder);
// Write the end of a cache debug block.
if (_cacheOptions.DebugMode)
{
writer.WriteLine();
writer.WriteLine($"<!-- END CACHE BLOCK: {cacheContext.CacheId} -->");
}
await writer.FlushAsync();
}
var html = sb.Builder.ToString();
var formattingContext = new DistributedCacheTagHelperFormattingContext
{
Html = new HtmlString(html)
};
await _dynamicCacheService.SetCachedValueAsync(cacheContext, html);
content = formattingContext.Html;
}
}
else
{
content = new HtmlString(value);
}
}
catch
{
content = null;
throw;
}
finally
{
// Remove the worker task before setting the result.
// If the result is null, other threads would potentially
// acquire it otherwise.
_dynamicCacheTagHelperService.Workers.TryRemove(CacheId, out result);
// Notify all other awaiters to render the content
tcs.TrySetResult(content);
}
}
else
{
content = await result;
}
}
return(content);
}
