94 lines
3.4 KiB
C#
94 lines
3.4 KiB
C#
using System;
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using System.Runtime.Remoting.Messaging;
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using Umbraco.Core;
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namespace Umbraco.Web
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{
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internal abstract class HybridAccessorBase<T>
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where T : class
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{
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// ReSharper disable StaticMemberInGenericType
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private static readonly object Locker = new object();
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private static bool _registered;
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// ReSharper restore StaticMemberInGenericType
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private readonly IHttpContextAccessor _httpContextAccessor;
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protected abstract string ItemKey { get; }
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// read
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// http://blog.stephencleary.com/2013/04/implicit-async-context-asynclocal.html
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// http://stackoverflow.com/questions/14176028/why-does-logicalcallcontext-not-work-with-async
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// http://stackoverflow.com/questions/854976/will-values-in-my-threadstatic-variables-still-be-there-when-cycled-via-threadpo
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// https://msdn.microsoft.com/en-us/library/dd642243.aspx?f=255&MSPPError=-2147217396 ThreadLocal<T>
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// http://stackoverflow.com/questions/29001266/cleaning-up-callcontext-in-tpl clearing call context
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//
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// anything that is ThreadStatic will stay with the thread and NOT flow in async threads
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// the only thing that flows is the logical call context (safe in 4.5+)
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// no!
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//[ThreadStatic]
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//private static T _value;
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// yes! flows with async!
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private T NonContextValue
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{
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get { return (T) CallContext.LogicalGetData(ItemKey); }
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set
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{
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if (value == null) CallContext.FreeNamedDataSlot(ItemKey);
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else CallContext.LogicalSetData(ItemKey, value);
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}
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}
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protected HybridAccessorBase(IHttpContextAccessor httpContextAccessor)
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{
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if (httpContextAccessor == null) throw new ArgumentNullException(nameof(httpContextAccessor));
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_httpContextAccessor = httpContextAccessor;
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lock (Locker)
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{
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// register the itemKey once with SafeCallContext
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if (_registered) return;
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_registered = true;
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}
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// ReSharper disable once VirtualMemberCallInConstructor
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var itemKey = ItemKey; // virtual
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SafeCallContext.Register(() =>
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{
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var value = CallContext.LogicalGetData(itemKey);
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CallContext.FreeNamedDataSlot(itemKey);
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return value;
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}, o =>
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{
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if (o == null) return;
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var value = o as T;
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if (value == null) throw new ArgumentException($"Expected type {typeof(T).FullName}, got {o.GetType().FullName}", nameof(o));
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CallContext.LogicalSetData(itemKey, value);
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});
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}
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protected T Value
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{
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get
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{
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var httpContext = _httpContextAccessor.HttpContext;
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if (httpContext == null) return NonContextValue;
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return (T) httpContext.Items[ItemKey];
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}
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set
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{
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var httpContext = _httpContextAccessor.HttpContext;
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if (httpContext == null)
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NonContextValue = value;
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else if (value == null)
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httpContext.Items.Remove(ItemKey);
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else
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httpContext.Items[ItemKey] = value;
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}
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}
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}
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}
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