HostExecutionContextManager.cs

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namespace System.Threading;
 
public class HostExecutionContextManager
{
    private sealed class HostExecutionContextSwitcher
    {
        public readonly HostExecutionContext _currentContext;
 
        public AsyncLocal<bool> _asyncLocal;
 
        public HostExecutionContextSwitcher(HostExecutionContext currentContext)
        {
            _currentContext = currentContext;
            _asyncLocal = new AsyncLocal<bool>();
            _asyncLocal.Value = true;
        }
    }
 
    [ThreadStatic]
    private static HostExecutionContext t_currentContext;
 
    public virtual HostExecutionContext? Capture()
    {
        return null;
    }
 
    public virtual object SetHostExecutionContext(HostExecutionContext hostExecutionContext)
    {
        if (hostExecutionContext == null)
        {
            throw new InvalidOperationException(System.SR.HostExecutionContextManager_InvalidOperation_NotNewCaptureContext);
        }
        HostExecutionContextSwitcher result = new HostExecutionContextSwitcher(hostExecutionContext);
        t_currentContext = hostExecutionContext;
        return result;
    }
 
    public virtual void Revert(object previousState)
    {
        if (!(previousState is HostExecutionContextSwitcher hostExecutionContextSwitcher))
        {
            throw new InvalidOperationException(System.SR.HostExecutionContextManager_InvalidOperation_CannotOverrideSetWithoutRevert);
        }
        if (t_currentContext != hostExecutionContextSwitcher._currentContext || hostExecutionContextSwitcher._asyncLocal == null || !hostExecutionContextSwitcher._asyncLocal.Value)
        {
            throw new InvalidOperationException(System.SR.HostExecutionContextManager_InvalidOperation_CannotUseSwitcherOtherThread);
        }
        hostExecutionContextSwitcher._asyncLocal = null;
        t_currentContext = null;
    }
}