104 lines
3.5 KiB
C#
104 lines
3.5 KiB
C#
using System;
|
|
using Umbraco.Core;
|
|
using Umbraco.Core.Cache;
|
|
using Umbraco.Core.Scoping;
|
|
|
|
namespace Umbraco.Web
|
|
{
|
|
/// <summary>
|
|
/// Provides a base class for hybrid accessors.
|
|
/// </summary>
|
|
/// <typeparam name="T">The type of the accessed object.</typeparam>
|
|
/// <remarks>
|
|
/// <para>Hybrid accessors store the accessed object in HttpContext if they can,
|
|
/// otherwise they rely on the logical call context, to maintain an ambient
|
|
/// object that flows with async.</para>
|
|
/// </remarks>
|
|
public abstract class HybridAccessorBase<T>
|
|
where T : class
|
|
{
|
|
private readonly IRequestCache _requestCache;
|
|
|
|
// ReSharper disable StaticMemberInGenericType
|
|
private static readonly object Locker = new object();
|
|
private static bool _registered;
|
|
// ReSharper restore StaticMemberInGenericType
|
|
|
|
protected abstract string ItemKey { get; }
|
|
|
|
// read
|
|
// http://blog.stephencleary.com/2013/04/implicit-async-context-asynclocal.html
|
|
// http://stackoverflow.com/questions/14176028/why-does-logicalcallcontext-not-work-with-async
|
|
// http://stackoverflow.com/questions/854976/will-values-in-my-threadstatic-variables-still-be-there-when-cycled-via-threadpo
|
|
// https://msdn.microsoft.com/en-us/library/dd642243.aspx?f=255&MSPPError=-2147217396 ThreadLocal<T>
|
|
// http://stackoverflow.com/questions/29001266/cleaning-up-callcontext-in-tpl clearing call context
|
|
//
|
|
// anything that is ThreadStatic will stay with the thread and NOT flow in async threads
|
|
// the only thing that flows is the logical call context (safe in 4.5+)
|
|
|
|
// no!
|
|
//[ThreadStatic]
|
|
//private static T _value;
|
|
|
|
// yes! flows with async!
|
|
private T NonContextValue
|
|
{
|
|
get => CallContext<T>.GetData(ItemKey);
|
|
set
|
|
{
|
|
CallContext<T>.SetData(ItemKey, value);
|
|
}
|
|
}
|
|
|
|
protected HybridAccessorBase(IRequestCache requestCache)
|
|
{
|
|
_requestCache = requestCache ?? throw new ArgumentNullException(nameof(requestCache));
|
|
|
|
lock (Locker)
|
|
{
|
|
// register the itemKey once with SafeCallContext
|
|
if (_registered) return;
|
|
_registered = true;
|
|
}
|
|
|
|
// ReSharper disable once VirtualMemberCallInConstructor
|
|
var itemKey = ItemKey; // virtual
|
|
SafeCallContext.Register(() =>
|
|
{
|
|
var value = CallContext<T>.GetData(itemKey);
|
|
return value;
|
|
}, o =>
|
|
{
|
|
if (o == null) return;
|
|
var value = o as T;
|
|
if (value == null) throw new ArgumentException($"Expected type {typeof(T).FullName}, got {o.GetType().FullName}", nameof(o));
|
|
CallContext<T>.SetData(itemKey, value);
|
|
});
|
|
}
|
|
|
|
protected T Value
|
|
{
|
|
get
|
|
{
|
|
if (!_requestCache.IsAvailable)
|
|
{
|
|
return NonContextValue;
|
|
}
|
|
return (T) _requestCache.Get(ItemKey);
|
|
}
|
|
|
|
set
|
|
{
|
|
if (!_requestCache.IsAvailable)
|
|
{
|
|
NonContextValue = value;
|
|
}
|
|
else if (value == null)
|
|
_requestCache.Remove(ItemKey);
|
|
else
|
|
_requestCache.Set(ItemKey, value);
|
|
}
|
|
}
|
|
}
|
|
}
|