/// <summary>
/// Queries the message source.
/// </summary>
/// <param name="source">The message source to query.</param>
/// <returns>Returns a task object.</returns>
private async Task RequestMessagesAsync(IMessageSource source)
{
Application.Current.AssertBackgroundThread();
await Application.Current.Dispatcher.InvokeAsync(() => _messages.Clear());
var messages = await source.GetMessagesAsync();
await Application.Current.Dispatcher.InvokeAsync(() => {
_messages.DeferNotifications = true;
_messages.AddRange(messages);
_messages.DeferNotifications = false;
_messages.NotifyCollectionChanged();
});
}