在MSDN上有一个非常好的非常简单的解决方案:

<TextBox
    MouseDoubleClick="SelectAddress"
    GotKeyboardFocus="SelectAddress"
    PreviewMouseLeftButtonDown="SelectivelyIgnoreMouseButton" />

下面是背后的代码:

private void SelectAddress(object sender, RoutedEventArgs e)
{
    TextBox tb = (sender as TextBox);
    if (tb != null)
    {
        tb.SelectAll();
    }
}

private void SelectivelyIgnoreMouseButton(object sender,
    MouseButtonEventArgs e)
{
    TextBox tb = (sender as TextBox);
    if (tb != null)
    {
        if (!tb.IsKeyboardFocusWithin)
        {
            e.Handled = true;
            tb.Focus();
        }
    }
}

我使用这个代码

  private void txtNav_GotFocus(object sender, RoutedEventArgs e)
            {
                e.Handled = true;
                var c = new DispatcherTimer();
                c.Interval = TimeSpan.FromMilliseconds(100);
                c.Tick += (a1, a2) =>
                {
                    c.IsEnabled = false;
                    txtNav.SelectAll();
                };
                c.IsEnabled = true;
    
            }

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();
}

对我来说，这是一个优秀的工作后，点击文本框上的鼠标:

private void TextBox_GotFocus(object sender, RoutedEventArgs e)
{
    Dispatcher.BeginInvoke(() => ((TextBox)sender).SelectAll());
    e.Handled = true;
}

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……

试着把这个放在你的文本框的任何控件的构造函数中:

Loaded += (sender, e) =>
{
    MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
    myTextBox.SelectAll();
}