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();
            }
        }
    }
}

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;
    
            }

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();
    }
}

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!

这对我来说似乎很有效。它基本上是一些早期帖子的重述。我只是把它放到构造函数的MainWindow.xaml.cs文件中。我创建了两个处理程序，一个用于键盘，一个用于鼠标，并将两个事件导入同一个函数HandleGotFocusEvent，该函数定义在同一个文件的构造函数之后。

public MainWindow()
{
   InitializeComponent();

   EventManager.RegisterClassHandler(typeof(TextBox), 
      UIElement.GotKeyboardFocusEvent,
      new RoutedEventHandler(HandleGotFocusEvent), true);
   EventManager.RegisterClassHandler(typeof(TextBox),
      UIElement.GotMouseCaptureEvent,
      new RoutedEventHandler(HandleGotFocusEvent), true);   
}
private void HandleGotFocusEvent(object sender, RoutedEventArgs e)
{
   if (sender is TextBox)
      (sender as TextBox).SelectAll();
}

我使用了Nils的答案，但将其转换为更灵活的答案。

public enum SelectAllMode
{

    /// <summary>
    ///  On first focus, it selects all then leave off textbox and doesn't check again
    /// </summary>
    OnFirstFocusThenLeaveOff = 0,

    /// <summary>
    ///  On first focus, it selects all then never selects
    /// </summary>
    OnFirstFocusThenNever = 1,

    /// <summary>
    /// Selects all on every focus
    /// </summary>
    OnEveryFocus = 2,

    /// <summary>
    /// Never selects text (WPF's default attitude)
    /// </summary>
    Never = 4,
}

public partial class TextBox : DependencyObject
{
    public static readonly DependencyProperty SelectAllModeProperty = DependencyProperty.RegisterAttached(
        "SelectAllMode",
        typeof(SelectAllMode?),
        typeof(TextBox),
        new PropertyMetadata(SelectAllModePropertyChanged));

    private static void SelectAllModePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is System.Windows.Controls.TextBox)
        {
            var textBox = d as System.Windows.Controls.TextBox;

            if (e.NewValue != null)
            {
                textBox.GotKeyboardFocus += OnKeyboardFocusSelectText;
                textBox.PreviewMouseLeftButtonDown += OnMouseLeftButtonDown;
            }
            else
            {
                textBox.GotKeyboardFocus -= OnKeyboardFocusSelectText;
                textBox.PreviewMouseLeftButtonDown -= OnMouseLeftButtonDown;
            }
        }
    }

    private static void OnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        DependencyObject dependencyObject = GetParentFromVisualTree(e.OriginalSource);

        if (dependencyObject == null)
            return;

        var textBox = (System.Windows.Controls.TextBox)dependencyObject;
        if (!textBox.IsKeyboardFocusWithin)
        {
            textBox.Focus();
            e.Handled = true;
        }
    }

    private static DependencyObject GetParentFromVisualTree(object source)
    {
        DependencyObject parent = source as UIElement;
        while (parent != null && !(parent is System.Windows.Controls.TextBox))
        {
            parent = VisualTreeHelper.GetParent(parent);
        }

        return parent;
    }

    private static void OnKeyboardFocusSelectText(object sender, KeyboardFocusChangedEventArgs e)
    {
        var textBox = e.OriginalSource as System.Windows.Controls.TextBox;
        if (textBox == null) return;

        var selectAllMode = GetSelectAllMode(textBox);

        if (selectAllMode == SelectAllMode.Never)
        {
            textBox.SelectionStart = 0;
            textBox.SelectionLength = 0;
        }
        else
            textBox.SelectAll();

        if (selectAllMode == SelectAllMode.OnFirstFocusThenNever)
            SetSelectAllMode(textBox, SelectAllMode.Never);
        else if (selectAllMode == SelectAllMode.OnFirstFocusThenLeaveOff)
            SetSelectAllMode(textBox, null);
    }

    [AttachedPropertyBrowsableForChildrenAttribute(IncludeDescendants = false)]
    [AttachedPropertyBrowsableForType(typeof(System.Windows.Controls.TextBox))]
    public static SelectAllMode? GetSelectAllMode(DependencyObject @object)
    {
        return (SelectAllMode)@object.GetValue(SelectAllModeProperty);
    }

    public static void SetSelectAllMode(DependencyObject @object, SelectAllMode? value)
    {
        @object.SetValue(SelectAllModeProperty, value);
    }
}

在XAML中，你可以这样使用:

<!-- On first focus, it selects all then leave off textbox and doesn't check again -->
<TextBox attprop:TextBox.SelectAllMode="OnFirstFocusThenLeaveOff" />

<!-- On first focus, it selects all then never selects -->
<TextBox attprop:TextBox.SelectAllMode="OnFirstFocusThenNever" />

<!-- Selects all on every focus -->
<TextBox attprop:TextBox.SelectAllMode="OnEveryFocus" />

<!-- Never selects text (WPF's default attitude) -->
<TextBox attprop:TextBox.SelectAllMode="Never" />