异步字符串赋值，GetAwaiter？

Question

我正在为WPF文本块分配一个大字符串，我想让它异步发生，甚至“流式”进入新位置。我很好奇我是否可以扩展字符串类以获得GetAwaiter（），任何想法？这不需要花哨，但我不喜欢它在分配大字符串时锁定的方式。

private async void listBoxSelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if (ready && listOfData.Count > 0 && listBox.SelectedIndex >= 0) // this prevents issues when called by reloading (which counts as selection change)
    {
        var idx = listBox.SelectedIndex;
        ResultBlock.Text = listOfData[idx]; // *** THIS IS WHAT I WANT TO HAPPEN ASYNC/PARALLEL/ETC
    }
}