在代码隐藏中更改 TextBox 中的文本时，它不会立即更新 [英] Text in a TextBox does not update instantly when change it in the code-behind

问题描述

在下面的简化代码中，我希望文本框在获取结果时说请稍候……".然而它从未出现，而是文本框只显示 functionThatTakesASecondOrTwoToRun()

In the simplified code below, I want the text box to say "Please wait.." while the result is being fetched. However it never appears, instead the textBox only displays the result of functionThatTakesASecondOrTwoToRun()

xml...

<Button Name="readDutButton" Content="Read DUT" Click="readDutButton_Click"/>
<TextBox Name="resultTextBox"/>

背后的代码......

code behind....

    private void readDutButton_Click(object sender, RoutedEventArgs e)
    {
        resultTextBox.Text = "Please wait...";   # this never appears

        result = functionThatTakesASecondOrTwoToRun();

        resultTextBox.Text = result;
    }

推荐答案

工作需要在后台线程中进行，例如

The work needs to happen in a background thread, e.g

resultTextBox.Text = "Please wait...";   // this never appears

Task.Factory.StartNew(() => functionThatTakesASecondOrTwoToRun())
.ContinueWith((t) => resultTextBox.Text = t.Result, 
TaskScheduler.FromCurrentSynchronizationContext());

由于 UI 阻塞了线程，因此 UI 没有进行更改以进行更新.TaskScheduler.FromCurrentSynchronizationContext() 因此 ContinueWith 在 UI 线程上执行并有权访问控件.

The UI is not getting a change to update as the the UI is blocking the thread. TaskScheduler.FromCurrentSynchronizationContext() so the ContinueWith is executed on the UI thread and has access to the controls.

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