我选择了部分Donnelle的答案(跳过双击)，因为我认为这更自然。然而，像grokies一样，我不喜欢创建派生类的需要。但我也不喜欢Grokys的OnStartup方法。我需要在“一般但不总是”的基础上这样做。

我已经实现了这作为一个附加的DependencyProperty，所以我可以设置local:SelectTextOnFocus。在xaml中Active =“True”。我觉得这种方式最令人愉快。

using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;

public class SelectTextOnFocus : DependencyObject
{
    public static readonly DependencyProperty ActiveProperty = DependencyProperty.RegisterAttached(
        "Active",
        typeof(bool),
        typeof(SelectTextOnFocus),
        new PropertyMetadata(false, ActivePropertyChanged));

    private static void ActivePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is TextBox)
        {
            TextBox textBox = d as TextBox;
            if ((e.NewValue as bool?).GetValueOrDefault(false))
            {
                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 = (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 TextBox))
        {
            parent = VisualTreeHelper.GetParent(parent);
        }

        return parent;
    }

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

    [AttachedPropertyBrowsableForChildrenAttribute(IncludeDescendants = false)]
    [AttachedPropertyBrowsableForType(typeof(TextBox))]
    public static bool GetActive(DependencyObject @object)
    {
        return (bool) @object.GetValue(ActiveProperty);
    }

    public static void SetActive(DependencyObject @object, bool value)
    {
        @object.SetValue(ActiveProperty, value);
    }
}

对于我的“一般但不总是”功能，我在(全局)文本框样式中将这个附件属性设置为True。这样，“选择文本”总是“打开”的，但我可以在每个文本框的基础上禁用它。

我发现这里给出的答案都没有模仿标准的Windows文本框。例如，尝试在文本框的最后一个字符和文本框右侧之间的空白区域单击。这里的大多数解决方案总是选择整个内容，这使得将文本添加到文本框非常困难。

我在这里给出的答案在这方面表现得更好。它是一个行为(因此它需要来自Blend SDK的System.Windows.Interactivity程序集)。也可以使用附加属性重写。

public sealed class SelectAllTextOnFocusBehavior : Behavior<TextBox>
{
    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.PreviewMouseLeftButtonDown += AssociatedObject_PreviewMouseLeftButtonDown;
    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.PreviewMouseLeftButtonDown -= AssociatedObject_PreviewMouseLeftButtonDown;
    }

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

        var textBox = parent as TextBox;
        Debug.Assert(textBox != null);

        if (textBox.IsFocused) return;

        textBox.SelectAll();
        Keyboard.Focus(textBox);
        e.Handled = true;
    }
}

这是基于我在这里找到的代码。

在App.xaml文件中:

<Application.Resources>
    <Style TargetType="TextBox">
        <EventSetter Event="GotKeyboardFocus" Handler="TextBox_GotKeyboardFocus"/>
    </Style>
</Application.Resources>

在App.xaml.cs文件中:

private void TextBox_GotKeyboardFocus(Object sender, KeyboardFocusChangedEventArgs e)
{
    ((TextBox)sender).SelectAll();
}

有了这段代码，你可以在你的应用程序中找到所有的文本框。

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();
    }
}

从这里开始:

在App.xaml.cs文件中注册全局事件处理程序:

protected override void OnStartup(StartupEventArgs e)
{
    EventManager.RegisterClassHandler(typeof(TextBox),TextBox.GotFocusEvent,
    new RoutedEventHandler(TextBox_GotFocus));

    base.OnStartup(e);
}

那么处理程序就像这样简单:

private void TextBox_GotFocus(object sender, RoutedEventArgs e)
{
    (sender as TextBox).SelectAll();
}

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;
}