97 lines
3.9 KiB
C#
97 lines
3.9 KiB
C#
using System;
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using System.Linq;
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using System.Collections.Generic;
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namespace Umbraco.Core
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{
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internal class SafeCallContext : IDisposable
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{
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private static readonly List<Func<object>> EnterFuncs = new List<Func<object>>();
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private static readonly List<Action<object>> ExitActions = new List<Action<object>>();
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private static int _count;
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private readonly List<object> _objects;
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private bool _disposed;
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public static void Register(Func<object> enterFunc, Action<object> exitAction)
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{
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if (enterFunc == null) throw new ArgumentNullException(nameof(enterFunc));
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if (exitAction == null) throw new ArgumentNullException(nameof(exitAction));
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lock (EnterFuncs)
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{
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if (_count > 0) throw new InvalidOperationException("Cannot register while some SafeCallContext instances exist.");
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EnterFuncs.Add(enterFunc);
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ExitActions.Add(exitAction);
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}
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}
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// tried to make the UmbracoDatabase serializable but then it leaks to weird places
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// in ReSharper and so on, where Umbraco.Core is not available. Tried to serialize
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// as an object instead but then it comes *back* deserialized into the original context
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// as an object and of course it breaks everything. Cannot prevent this from flowing,
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// and ExecutionContext.SuppressFlow() works for threads but not domains. and we'll
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// have the same issue with anything that toys with logical call context...
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//
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// so this class lets anything that uses the logical call context register itself,
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// providing two methods:
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// - an enter func that removes and returns whatever is in the logical call context
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// - an exit action that restores the value into the logical call context
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// whenever a SafeCallContext instance is created, it uses these methods to capture
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// and clear the logical call context, and restore it when disposed.
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//
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// in addition, a static Clear method is provided - which uses the enter funcs to
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// remove everything from logical call context - not to be used when the app runs,
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// but can be useful during tests
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//
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// note
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// see System.Transactions
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// pre 4.5.1, the TransactionScope would not flow in async, and then then introduced
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// an option to store in in the LLC so that it flows
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// they are using a conditional weak table to store the data, and what they store in
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// LLC is the key - which is just an empty MarshalByRefObject that is created with
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// the transaction scope - that way, they can "clear current data" provided that
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// they have the key - but they need to hold onto a ref to the scope... not ok for us
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public static void Clear()
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{
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lock (EnterFuncs)
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{
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foreach (var enter in EnterFuncs)
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enter();
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}
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}
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public SafeCallContext()
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{
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lock (EnterFuncs)
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{
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_count++;
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_objects = EnterFuncs.Select(x => x()).ToList();
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}
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}
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public void Dispose()
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{
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if (_disposed) throw new ObjectDisposedException("this");
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_disposed = true;
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lock (EnterFuncs)
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{
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for (var i = 0; i < ExitActions.Count; i++)
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ExitActions[i](_objects[i]);
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_count--;
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}
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}
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// for unit tests ONLY
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internal static void Reset()
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{
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lock (EnterFuncs)
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{
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if (_count > 0) throw new InvalidOperationException("Cannot reset while some SafeCallContext instances exist.");
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EnterFuncs.Clear();
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ExitActions.Clear();
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}
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}
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}
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}
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