如何使C＃按钮仅单击一次并使文本框显示两个结果？

Question

I write below simple code. I want to make this happen: 1. Click button. 2. Show the first string. 3. Wait for 3 seconds. 4. Show the second string. But with this code, i can only see the second string after i click the button and wait for 3 seconds. i can't see the first string. is there any way to make this happen?

namespace clicktest
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {

        public MainWindow()
        {
            InitializeComponent();
        }
        private void button_Click(object sender, RoutedEventArgs e)
        {
            this.textBox.Text = "Show 1st time";
            Thread.Sleep(3000);
            this.textBox.Text = "Show 2nd time";
        }
    }
}

Answer 1

Blocking a thread, such as when using Thread.Sleep , in WPF prevents the GUI from refreshing.

Instead you can use await Task.Delay which won't block the thread:

private async void button_Click(object sender, RoutedEventArgs e)
{
    this.textBox.Text = "Show 1st time";
    await Task.Delay(3000);
    this.textBox.Text = "Show 2nd time";
}

Answer 2

As @Alexander Higgins said, you can use await Task.Delay , but you have to add the async type to your method, like this:

private async void button_Click(object sender, RoutedEventArgs e)
{
    this.textBox.Text = "Show 1st time";
    await Task.Delay(3000);
    this.textBox.Text = "Show 2nd time";
}