WPF 延迟异步更新 UI 控件？

Question

public void TextChangedEvent(object sender, EventArgs e)
        {
            TextBox changedTextBox = sender as TextBox;
            List<TextBox> textBoxes = new List<TextBox>();
            //gets Grid that contains all the textboxes
            var parentGrid = VisualHierarchyHelper.FindParent<Grid>(changedTextBox);
            var mainGrid = VisualHierarchyHelper.FindParent<Grid>(parentGrid);
            //ALL 81 textboxes
            var textBoxChildren = VisualHierarchyHelper.FindVisualChildren<TextBox>(mainGrid).ToList();
            for (int i = 0; i < textBoxChildren.Count; i++)
            {
                SendWithDelay(textBoxChildren[i]);
            }
        }

        async Task SendWithDelay(TextBox txt)
        {
            await Task.Delay(1000);
            txt.Background = Brushes.Red;
        }

I want 81 grids to get a red background 1 by one, now it just waits a bit and updates everything at once.

Any suggestions?

Note: This code is runnable but it does complain about SendWithDelay(textBoxChildren[i]); not being awaited, if I change this and also change void to async Task it says Error CS0407 'Task EventHandling.TextChangedEvent(object, EventArgs)' has the wrong return type .

EDIT

This is what I have now:

public void TextChangedEvent(object sender, EventArgs e)
        {
            TextBox changedTextBox = sender as TextBox;
            List<TextBox> textBoxes = new List<TextBox>();
            //gets Grid that contains all the textboxes
            var parentGrid = VisualHierarchyHelper.FindParent<Grid>(changedTextBox);
            var mainGrid = VisualHierarchyHelper.FindParent<Grid>(parentGrid);
            //ALL 81 textboxes
            var textBoxChildren = VisualHierarchyHelper.FindVisualChildren<TextBox>(mainGrid).ToList();
            for (int i = 0; i < textBoxChildren.Count; i++)
            {
                x SendWithDelay(textBoxChildren[i]);
            }
        }

        async void SendWithDelay(TextBox txt)
        {
            txt.Background = Brushes.Red;   
            x await Task.Delay(500);
        } 

The breakpoints(x) just alternate between each other. Then when they're done everything gets red.

Answer 1

You can make make TextChangedEvent async:

public async void TextChangedEvent(object sender, EventArgs e) {

And await the call to SendWithDelay :

await SendWithDelay(textBoxChildren[i]);

It'll get rid of all the warnings you're getting, but it seems like you want SendWithDelay to be "Fire and forget", this way you can change SendWithDelay to async void instead of async Task :

async Task SendWithDelay(TextBox txt) {

And not await every call to it:

SendWithDelay(textBoxChildren[i]);

Answer 2

1 second Delay

async Task LongRunningProcess()
{

    await Task.Delay(1000);

}

In your loop

public async void TextChangedEvent(object sender, EventArgs e)
{
  for (int i = 0; i < textBoxChildren.Count; i++)
  {
     txt.Background = Brushes.Red;
     await Task.Run(() => LongRunningProcess());
  }
}