最简单和完美的解决方案，是在文本框获得焦点后使用计时器选择所有文本20ms:

Dim WithEvents Timer作为新的DispatcherTimer()

设置间隔: 计时器。Interval = timspan . frommilliseconds (20)

响应事件(我在这里继承了TextBox控件，所以我重写了它的事件:

Protected Overrides Sub OnGotFocus(e As RoutedEventArgs)
        Timer.Start()
        MyBase.OnGotFocus(e)
    End Sub


    Private Sub Timer_Tick(sender As Object, e As EventArgs) Handles Timer.Tick
        Timer.Stop()
        Me.SelectAll()
    End Sub

这就是全部!

以下是@Nasenbaer发布的答案的c#版本

private delegate void TextBoxSelectAllDelegate(object sender);

private void TextBoxSelectAll(object sender)
{
    (sender as System.Windows.Controls.TextBox).SelectAll();
}

private void MyTextBox_GotFocus(object sender, System.Windows.RoutedEventArgs e)
{
    TextBoxSelectAllDelegate d = TextBoxSelectAll;

    this.Dispatcher.BeginInvoke(d,
        System.Windows.Threading.DispatcherPriority.ApplicationIdle, sender);
}

而MyTextBox_GotFocus是分配给MyTextBox的GotFocus事件的事件处理程序。

我以为这样简单多了。

nameOfTextbox.Focus();
nameOfTextbox.Select(0, nameOfTextbox.Text.Length);

同样，如果别人有你的光标不聚焦在文本框的问题，你可以使用这个在nameOfTextbox.Focus();以上。

Dispatcher.BeginInvoke(DispatcherPriority.Input,
new Action(delegate () {
    nameOfTextbox.Focus();         // Set Logical Focus
    Keyboard.Focus(nameOfTextbox); // Set Keyboard Focus
}));

我已经测试了所有的，但只有以下工作:

protected override void OnStartup(StartupEventArgs e) 
{
    EventManager.RegisterClassHandler(typeof(TextBox), UIElement.PreviewMouseLeftButtonDownEvent,
   new MouseButtonEventHandler(SelectivelyHandleMouseButton), true);
    EventManager.RegisterClassHandler(typeof(TextBox), UIElement.GotKeyboardFocusEvent,
      new RoutedEventHandler(SelectAllText), true);
    EventManager.RegisterClassHandler(typeof(TextBox), UIElement.GotFocusEvent,
      new RoutedEventHandler(GotFocus), true);          
}

private static void SelectivelyHandleMouseButton(object sender, MouseButtonEventArgs e)
{
    var textbox = (sender as TextBox);
    if (textbox != null)
    {
        int hc = textbox.GetHashCode();
        if (hc == LastHashCode)
        {
            if (e.OriginalSource.GetType().Name == "TextBoxView")
            {
                e.Handled = true;
                textbox.Focus();
                LastHashCode = -1;
            }
        }
    }
    if (textbox != null) textbox.Focus();
}

private static void SelectAllText(object sender, RoutedEventArgs e)
{
    var textBox = e.OriginalSource as TextBox;
    if (textBox != null)
        textBox.SelectAll();
}

private static int LastHashCode;
private static void GotFocus(object sender, RoutedEventArgs e)
{
    var textBox = e.OriginalSource as TextBox;
    if (textBox != null)
        LastHashCode = textBox.GetHashCode();
}

哇!读完以上所有内容后，我发现自己不知所措。我从这篇文章中学到了一些东西，并尝试了一些完全不同的东西。当文本框获得焦点时，我使用这个来选择文本:

private void TextField_GotFocus(object sender, RoutedEventArgs e)
{
    TextBox tb = (sender as Textbox);
    if(tb != null)
    {
        e.Handled = true;
        tb.Focus();
        tb.SelectAll();
    }
}

将文本框的GotFocus属性设置为该方法。

运行应用程序并在文本框中单击一次，将突出显示文本框中已经存在的所有内容。

如果目标确实是在用户单击文本框时选择文本，这看起来很简单，涉及的代码也少了很多。只是说……

不知道为什么它在GotFocus事件中失去了选择。

但是一个解决方案是在GotKeyboardFocus和GotMouseCapture事件上进行选择。这样它就能一直工作。

——编辑——

在这里添加一个例子来告诉人们如何解决上面提到的一些缺点:

private void TextBox_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    // Fixes issue when clicking cut/copy/paste in context menu
    if (textBox.SelectionLength == 0) 
        textBox.SelectAll();
}

private void TextBox_LostMouseCapture(object sender, MouseEventArgs e)
{
    // If user highlights some text, don't override it
    if (textBox.SelectionLength == 0) 
        textBox.SelectAll();

    // further clicks will not select all
    textBox.LostMouseCapture -= TextBox_LostMouseCapture; 
}

private void TextBox_LostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    // once we've left the TextBox, return the select all behavior
    textBox.LostMouseCapture += TextBox_LostMouseCapture;
}