Get WinForm "Cross-thread operation not valid" error for WCF host application ONLY while running in Visual Studio - winforms

Question

I have a WCF service that I am self-hosting in a WinForm application. In the application I have a ListBox control to display diagnostic information. I pass a reference to the ListBox control to the WCF service. In that service there is a callback that uses it.
For some reason if I run the application outside of Visual Studio, I am able to use the ListBox to display information in the main hosting application, all methods in the WCF service, and the single callback in the WCF service. But, running in Visual Studio, the same application fails when trying to write info while in the callback.
Am I doing something that I fundamentally cannot do and getting away with it OR is there something incorrect going on while running in Visual Studio?
Here is part of my WinForm host
public WCFServiceHostGUI()
{
InitializeComponent();
// OutputBox is a ListBox control reference. Pass to WCF service to display diagnostics
WCFCallbacks.UsbBrokerService.initialize(OutputBox);
startService();
}
private void startService()
{
usbBrokerServiceHost = new ServiceHost(typeof(WCFCallbacks.UsbBrokerService));
ServiceDescription serviceDesciption = usbBrokerServiceHost.Description;
foreach (ServiceEndpoint endpoint in serviceDesciption.Endpoints)
{
OutputBox.Items.Add("Endpoint - address: " + endpoint.Address);
OutputBox.Items.Add(" - binding name: " + endpoint.Binding.Name);
OutputBox.Items.Add(" - contract name: " + endpoint.Contract.Name);
}
usbBrokerServiceHost.Open();
/*
ChannelFactory<WCFCallbacks.IUsbBroker> channelFactory = new ChannelFactory<WCFCallbacks.IUsbBroker>(BINDING, ADDRESS);
WCFCallbacks.IUsbBroker clientProxy = channelFactory.CreateChannel();
clientProxy.initialize(OutputBox);
*/
}
In the constructor a reference to the ListBox is passed to the WCF service. One can see the usual creation of the ServiceHost in the startService() method.
Here is the WCF service that gets the ListBox reference
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
public class UsbBrokerService : IUsbBroker
{
private static readonly List<IUsbBrokerCallback> subscribers = new List<IUsbBrokerCallback>();
private static ListBox OutputBox = null;
public UsbBrokerService()
{
Console.WriteLine("Service started");
UsbDevicePluginIndicator.DeviceNotify += new UsbDevicePluginIndicator.DeviceNotifyDelegate(UsbDevicePluginIndicator_DeviceNotify);
UsbDevicePluginIndicator.Start();
}
public static void initialize(ListBox outputBox)
{
OutputBox = outputBox;
}
public void AddMessage(string message)
{
// Use the following to see which endpoint is accessed
OperationContext oc = OperationContext.Current;
if (oc != null)
{
Console.WriteLine("A request was made on endpoint " + oc.Channel.LocalAddress.ToString());
if (OutputBox != null)
{
OutputBox.Items.Add("A request was made on endpoint " + oc.Channel.LocalAddress.ToString());
}
}
}
public bool RegisterDevices(UsbDevice[] usbDevices)
{
try
{
IUsbBrokerCallback callback = OperationContext.Current.GetCallbackChannel<IUsbBrokerCallback>();
if (!subscribers.Contains(callback))
{
subscribers.Add(callback);
}
return true;
}
catch
{
return false;
}
}
public bool UnRegisterDevices(UsbDevice[] usbDevices)
{
try
{
IUsbBrokerCallback callback = OperationContext.Current.GetCallbackChannel<IUsbBrokerCallback>();
if (subscribers.Contains(callback))
{
subscribers.Remove(callback);
}
return true;
}
catch
{
return false;
}
}
private void UsbDevicePluginIndicator_DeviceNotify(System.Windows.Forms.Message msg)
{
BroadcastHeader lBroadcastHeader;
Console.WriteLine("Wcf WM_DEVICECHANGE signaled");
if (OutputBox != null)
{
OutputBox.Items.Add("Wcf WM_DEVICECHANGE signaled");
}
}
}
In the callback routine UsbDevicePluginIndicator_DeviceNotify the attempt to write to OutputBox fails with "Cross-thread operation not valid: Control 'OutputBox' accessed from a thread other than the thread it was created on." but ONLY while running in Visual Studio.
So am I doing something fundamentally wrong?