尝试这个扩展方法，添加所需的行为到任何文本框控件。我还没有对它进行广泛测试，但它似乎满足了我的需求。

public static class TextBoxExtensions
{
    public static void SetupSelectAllOnGotFocus(this TextBox source)
    {
        source.GotFocus += SelectAll;
        source.PreviewMouseLeftButtonDown += SelectivelyIgnoreMouseButton;
    }

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

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

Donnelle的答案是最好的，但是必须派生一个新的类来使用它是一种痛苦。

我没有这样做，而是在App.xaml.cs中为应用程序中的所有文本框注册处理程序。这允许我使用一个标准的文本框控件唐纳利的答案。

在App.xaml.cs中添加以下方法:

public partial class App : Application
{
    protected override void OnStartup(StartupEventArgs e) 
    {
        // Select the text in a TextBox when it receives focus.
        EventManager.RegisterClassHandler(typeof(TextBox), TextBox.PreviewMouseLeftButtonDownEvent,
            new MouseButtonEventHandler(SelectivelyIgnoreMouseButton));
        EventManager.RegisterClassHandler(typeof(TextBox), TextBox.GotKeyboardFocusEvent, 
            new RoutedEventHandler(SelectAllText));
        EventManager.RegisterClassHandler(typeof(TextBox), TextBox.MouseDoubleClickEvent,
            new RoutedEventHandler(SelectAllText));
        base.OnStartup(e); 
    }

    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 focused, give it the focus and
                // stop further processing of this click event.
                textBox.Focus();
                e.Handled = true;
            }
        }
    }

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

一个简单的方法来覆盖鼠标向下和选择所有双击后:

public class DoubleClickTextBox: TextBox
{

    public override void EndInit()
    {
        base.EndInit();            
    }

    protected override void OnMouseEnter(System.Windows.Input.MouseEventArgs e)
    {
        base.OnMouseEnter(e);
        this.Cursor = Cursors.Arrow;
    }
    protected override void OnMouseDown(System.Windows.Input.MouseButtonEventArgs e)
    {

    }

    protected override void OnMouseDoubleClick(System.Windows.Input.MouseButtonEventArgs e)
    {
        base.OnMouseDown(e);
        this.SelectAll();
    }
}

我搜索了很多解决方案，我发现了两个解决方案选择但是，问题是，当我们做右键单击，并从文本框选择部分文本后进行剪切/复制，它选择了所有甚至我选择了部分文本。解决办法就在这里。只需在键盘选择事件中添加以下代码。这对我很管用。

private static void SelectContentsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    if (d is TextBox)
    {
        TextBox textBox = d as TextBox;
        if ((e.NewValue as bool?).GetValueOrDefault(false))
        {
            textBox.GotKeyboardFocus += OnKeyboardFocusSelectText;                 
        }
        else
        {
            textBox.GotKeyboardFocus -= OnKeyboardFocusSelectText;

        }
    }
}


private static void OnKeyboardFocusSelectText(object sender, KeyboardFocusChangedEventArgs e)
{
    if (e.KeyboardDevice.IsKeyDown(Key.Tab))
        ((TextBox)sender).SelectAll();
}

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
}));