我正在做async / await吗？

Question

I'm trying to use async and await keywords for the first time and I have a doubt whether I'm doing this correctly.

In my WPF form's Loaded event I use a method:

private void MessagesWindowLoaded(object sender, RoutedEventArgs e)
{
    DataGridMessagesLoadAsync();
}

Which looks like this:

private async void DataGridMessagesLoadAsync()
{
    _messages = await _messageService.GetAllMessagesAsync();
    dataGridMessages.ItemsSource = _messages;
    if (_messages.Count() == 0) return;
    dataGridMessages.Columns[6].Visibility = System.Windows.Visibility.Collapsed;
    dataGridMessages.Columns[8].Visibility = System.Windows.Visibility.Collapsed;
    dataGridMessages.Columns[10].Visibility = System.Windows.Visibility.Collapsed;
    dataGridMessages.Columns[11].Visibility = System.Windows.Visibility.Collapsed;
    dataGridMessages.Columns[12].Visibility = System.Windows.Visibility.Collapsed;
}

The GetAllMessagesAsync() looks like this:

public async Task<List<Message>> GetAllMessagesAsync()
{
    return (from m in _context.Messages select m).ToList();
}

I'm not sure whether I get any asynchrony - it seems like the whole window is waiting for the DataGrid , but my data is so small that I can't figure out whether it's just my computer lag or really the DataGrid . What's more, Visual Studio gives a warning:

This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.

So I understand I would have to await something in GetAllMessagesAsync() ? But what? And the new function would have to await some other async function as well? I can't figure it out, I get into an infinite loop in my mind.

Answer 1

You can just return a Task directly:

public Task<List<Message>> GetAllMessagesAsync()
{
    return Task.Factory.StartNew(() => _context.Messages.ToList());
}