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();
}

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
}));

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;
}

我们有它，所以第一次点击选择所有，另一次点击光标(我们的应用程序是设计用于平板电脑与笔)。

你可能会发现它很有用。

public class ClickSelectTextBox : TextBox
{
    public ClickSelectTextBox()
    {
        AddHandler(PreviewMouseLeftButtonDownEvent, 
          new MouseButtonEventHandler(SelectivelyIgnoreMouseButton), true);
        AddHandler(GotKeyboardFocusEvent, 
          new RoutedEventHandler(SelectAllText), true);
        AddHandler(MouseDoubleClickEvent, 
          new RoutedEventHandler(SelectAllText), true);
    }

    private static void SelectivelyIgnoreMouseButton(object sender, 
                                                     MouseButtonEventArgs e)
    {
        // Find the TextBox
        DependencyObject parent = e.OriginalSource as UIElement;
        while (parent != null && !(parent is TextBox))
            parent = VisualTreeHelper.GetParent(parent);

        if (parent != null)
        {
            var textBox = (TextBox)parent;
            if (!textBox.IsKeyboardFocusWithin)
            {
                // If the text box is not yet focussed, give it the focus and
                // stop further processing of this click event.
                textBox.Focus();
                e.Handled = true;
            }
        }
    }

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

我也有同样的问题。在VB。Net的工作方式很简单:

VB XAML:

<TextBox x:Name="txtFilterFrequency" />

Codehind:

Private Sub txtFilterText_GotFocus(sender As System.Object, e As System.Windows.RoutedEventArgs) Handles txtFilterText.GotFocus
    Me.Dispatcher.BeginInvoke(Sub()
                                  txtFilterText.SelectAll()
                              End Sub, DispatcherPriority.ApplicationIdle, Nothing)
End Sub

c#(感谢ViRuSTriNiTy)

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);
}

我对此有一个稍微简化的答案(只有PreviewMouseLeftButtonDown事件)，这似乎模仿了浏览器的常用功能:

在XAML中，你有一个文本框说:

<TextBox Text="http://www.blabla.com" BorderThickness="2" BorderBrush="Green" VerticalAlignment="Center" Height="25"
                 PreviewMouseLeftButtonDown="SelectAll" />

在后台代码:

private void SelectAll(object sender, MouseButtonEventArgs e)
{
    TextBox tb = (sender as TextBox);

    if (tb == null)
    {
        return;
    }

    if (!tb.IsKeyboardFocusWithin)
    {
        tb.SelectAll();
        e.Handled = true;
        tb.Focus();
    }
}