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public int Disconnect(int millisecondsTimeout = Timeout.Infinite)
{
	if (_gattClient.State != wclClientState.csConnecting && 
        _gattClient.State!=wclClientState.csConnected)
		throw new InvalidOperationException("The client is not connected");
	int result = 0;
	using (var ev = new AutoResetEvent(false))
	{
        // must use a lambda for this because we need to hoist due to lack of a state value
		wclClientConnectionDisconnectEvent cde = (object sender, int reason) =>
		{
            // set the result
			result = reason;
            // signal completion
			ev.Set();
		};
        // add the event handler
		_gattClient.OnDisconnect += cde;
        // call disconnect and throw on error result
		BleException.Check(_gattClient.Disconnect());
        // wait for the event to fire
		if (!ev.WaitOne(millisecondsTimeout))
			throw new TimeoutException("The disconnect operation timed out");
        // remove the event handler
		_gattClient.OnDisconnect -= cde;
	}
	return result;
}

// necessary for the disconnect event handler to remove *itself* from the event when it's done
wclClientConnectionDisconnectEvent _cdeHandler;

public Task<int> DisconnectAsync()
{
	if (_gattClient.State != wclClientState.csConnecting && 
		_gattClient.State != wclClientState.csConnected)
		throw new InvalidOperationException("The client is not connected");
    // this gets fun
	var tcs = new TaskCompletionSource<int>();
    // sanity check
	System.Diagnostics.Debug.Assert(null == _cdeHandler,"The async disconnect was somehow already in progress");
    // must use a lambda here because we need hoisting due to lack of a state argument
	_cdeHandler = (object sender, int reason) =>
	{
        // set the task to completed and give it the result
		tcs.SetResult(reason);
        // remove the event handler. We had to use a member field
        // to store the handler so we could find it within itself
		_gattClient.OnDisconnect -= _cdeHandler;
        // we're done with it for now, until the next time this is called
		_cdeHandler = null;
	};
    // add our event handler
	_gattClient.OnDisconnect += _cdeHandler;
    // attempt to disconnect and throw on unsuccessful
	BleException.Check(_gattClient.Disconnect());
    // return the task
	return tcs.Task;
}