ProximityMessage class

public sealed class ProximityMessage : Object

Windows.Networking.Proximity.ProximityDevice proximityDevice;
long publishedMessageId = -1;
long subscribedMessageId = -1;

private void initializeProximityDevice()
{
    proximityDevice = Windows.Networking.Proximity.ProximityDevice.GetDefault();

    if (proximityDevice != null)
    {
        PublishMessageButton.Click += PublishMessage;
        SubscribeForMessageButton.Click += SubscribeForMessage;
        StopSubscribingForMessageButton.Click += StopSubscribingForMessage;
        StopPublishingMessageButton.Click += StopPublishingMessage;
    }
    else
    {
        WriteMessageText("Failed to initialized proximity device.\n");
    }
}

private void PublishMessage(object sender, RoutedEventArgs e)
{
    // Stop publishing the current message.
    if (publishedMessageId != -1)
    {
        proximityDevice.StopPublishingMessage(publishedMessageId);
    }

    publishedMessageId = 
        proximityDevice.PublishMessage("Windows.SampleMessage", MessageTextBlock.Text);
}

private void SubscribeForMessage(object sender, RoutedEventArgs e)
{
    // Only subscribe for the message one time.
    if (subscribedMessageId == -1)
    {
        subscribedMessageId = 
        proximityDevice.SubscribeForMessage("Windows.SampleMessage", messageReceived);
    }
}

private void messageReceived(
    Windows.Networking.Proximity.ProximityDevice device, 
    Windows.Networking.Proximity.ProximityMessage message)
{
    MessageBlock.Text += "Message received: " + message.DataAsString + "\n";
}

private void StopSubscribingForMessage(object sender, RoutedEventArgs e)
{
    proximityDevice.StopSubscribingForMessage(subscribedMessageId);
    subscribedMessageId = -1;
}

private void StopPublishingMessage(object sender, RoutedEventArgs e)
{
    proximityDevice.StopPublishingMessage(publishedMessageId);
    publishedMessageId = -1;
}

// Write a message to MessageBlock on the UI thread.
private Windows.UI.Core.CoreDispatcher messageDispatcher = Window.Current.CoreWindow.Dispatcher;

async private void WriteMessageText(string message, bool overwrite = false)
{
    await messageDispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        () =>
        {
            if (overwrite)
                MessageBlock.Text = message;
            else
                MessageBlock.Text += message;
        });
}