private void GetDataToList()
{
  Stopwatch watch = new Stopwatch();
  using (var ctx = new Context())
  {
    watch.Start();
    dg.ItemsSource = ctx.Items.AsNoTracking().ToList();
    watch.Stop();
    MessageBox.Show(watch.Elapsed.ToString());
  }
}

private async void GetDataTaskRun()
{
  Stopwatch watch = new Stopwatch();
  using (var ctx = new Context())
  {
    watch.Start();
    dg.ItemsSource = await Task.Run(() => ctx.Items.AsNoTracking().ToList());
    watch.Stop();
    MessageBox.Show(watch.Elapsed.ToString());
  }
}

private async void GetDataToListAsync()
{
  Stopwatch watch = new Stopwatch();
  using (var ctx = new Context())
  {
    watch.Start();
    dg.ItemsSource = await ctx.Items.AsNoTracking().ToListAsync();
    watch.Stop();
    MessageBox.Show(watch.Elapsed.ToString());
  }
}