如果我从GotFocus事件处理程序中调用SelectAll，使用鼠标操作时它不起作用-选择会在鼠标释放时消失。
编辑：人们喜欢Donnelle的答案，我试图解释为什么我不像已被接受的答案那样喜欢它。
我们这样做是为了第一次点击时全选，再次点击将光标移到指定位置（我们的应用程序设计用于使用带笔的平板电脑）。
你可能会觉得这很有用。
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();
}
}
textBox.IsFocused 的 SelectAllText 方法中增加一个测试可以改善它。当 GetKeyboardFocus 是由于通过 alt-tab 切换到程序时，您不希望选择全部内容。 - Scott StaffordDonnelle的答案效果最好，但是必须派生一个新类来使用它有点麻烦。
相反，我在App.xaml.cs中为应用程序中的所有TextBox注册处理程序。这使我能够在标准TextBox控件中使用Donnelle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();
}
}
我选择了Donnelle的答案的一部分（跳过了双击），因为我认为这更自然。然而，像Grokys一样，我不喜欢需要创建派生类的需求。但是我也不喜欢Grokys的OnStartup方法。而且我需要它是“通常但不总是”的基础。
我已经将其实现为附加的DependencyProperty，所以我可以在xaml中设置local:SelectTextOnFocus.Active = "True"。我发现这种方式最令人愉悦。
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);
}
}
为了实现我的“通常但不总是”功能，我在（全局）TextBoxStyle中将此附加属性设置为True。这样，“选择文本”始终处于“开启”状态，但我可以在每个文本框上禁用它。
不知道为什么在 GotFocus 事件中会失去选择。
但是一种解决方法是在 GotKeyboardFocus 和 GotMouseCapture 事件中进行选择。这样它总是有效的。
-- 编辑 --
在此添加一个示例，以向人们展示如何解决其中提到的一些缺点：
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;
}
以下是实现答案解决方案的混合行为，供您参考：
一个用于附加到单个文本框的混合行为：
public class SelectAllTextOnFocusBehavior : Behavior<TextBox>
{
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.GotKeyboardFocus += AssociatedObjectGotKeyboardFocus;
AssociatedObject.GotMouseCapture += AssociatedObjectGotMouseCapture;
AssociatedObject.PreviewMouseLeftButtonDown += AssociatedObjectPreviewMouseLeftButtonDown;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.GotKeyboardFocus -= AssociatedObjectGotKeyboardFocus;
AssociatedObject.GotMouseCapture -= AssociatedObjectGotMouseCapture;
AssociatedObject.PreviewMouseLeftButtonDown -= AssociatedObjectPreviewMouseLeftButtonDown;
}
private void AssociatedObjectGotKeyboardFocus(object sender,
System.Windows.Input.KeyboardFocusChangedEventArgs e)
{
AssociatedObject.SelectAll();
}
private void AssociatedObjectGotMouseCapture(object sender,
System.Windows.Input.MouseEventArgs e)
{
AssociatedObject.SelectAll();
}
private void AssociatedObjectPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
if(!AssociatedObject.IsKeyboardFocusWithin)
{
AssociatedObject.Focus();
e.Handled = true;
}
}
}
另外还有一个用于附加到包含多个文本框的容器根部的方法：
public class SelectAllTextOnFocusMultiBehavior : Behavior<UIElement>
{
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.GotKeyboardFocus += HandleKeyboardFocus;
AssociatedObject.GotMouseCapture += HandleMouseCapture;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.GotKeyboardFocus -= HandleKeyboardFocus;
AssociatedObject.GotMouseCapture -= HandleMouseCapture;
}
private static void HandleKeyboardFocus(object sender,
System.Windows.Input.KeyboardFocusChangedEventArgs e)
{
var txt = e.NewFocus as TextBox;
if (txt != null)
txt.SelectAll();
}
private static void HandleMouseCapture(object sender,
System.Windows.Input.MouseEventArgs e)
{
var txt = e.OriginalSource as TextBox;
if (txt != null)
txt.SelectAll();
}
}
SelectAllTextOnFocusBehavior 工作得很好，但是 SelectAllTextOnFocusMultiBehavior 存在与问题中相同的问题。我尝试通过添加 PreviewMouseLeftButtonDown 来修复它，但是它似乎没有被触发... 只有当你点击文本后面而不是文本中时，它才会被正确地选择。 - KCT我使用了一个Attached Behavior来解决这个问题，而不是像Sergey的回答中那样使用Expression Behavior。这意味着我不需要在Blend SDK中依赖于System.Windows.Interactivity:
public class TextBoxBehavior
{
public static bool GetSelectAllTextOnFocus(TextBox textBox)
{
return (bool)textBox.GetValue(SelectAllTextOnFocusProperty);
}
public static void SetSelectAllTextOnFocus(TextBox textBox, bool value)
{
textBox.SetValue(SelectAllTextOnFocusProperty, value);
}
public static readonly DependencyProperty SelectAllTextOnFocusProperty =
DependencyProperty.RegisterAttached(
"SelectAllTextOnFocus",
typeof (bool),
typeof (TextBoxBehavior),
new UIPropertyMetadata(false, OnSelectAllTextOnFocusChanged));
private static void OnSelectAllTextOnFocusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var textBox = d as TextBox;
if (textBox == null) return;
if (e.NewValue is bool == false) return;
if ((bool) e.NewValue)
{
textBox.GotFocus += SelectAll;
textBox.PreviewMouseDown += IgnoreMouseButton;
}
else
{
textBox.GotFocus -= SelectAll;
textBox.PreviewMouseDown -= IgnoreMouseButton;
}
}
private static void SelectAll(object sender, RoutedEventArgs e)
{
var textBox = e.OriginalSource as TextBox;
if (textBox == null) return;
textBox.SelectAll();
}
private static void IgnoreMouseButton(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
var textBox = sender as TextBox;
if (textBox == null || (!textBox.IsReadOnly && textBox.IsKeyboardFocusWithin)) return;
e.Handled = true;
textBox.Focus();
}
}
然后您可以这样在XAML中使用它:
<TextBox Text="Some Text" behaviors:TextBoxBehavior.SelectAllTextOnFocus="True"/>
我在这里写了一篇关于它的博客（链接）。
这里有一个非常好的、非常简单的解决方案，来自于MSDN：
<TextBox
MouseDoubleClick="SelectAddress"
GotKeyboardFocus="SelectAddress"
PreviewMouseLeftButtonDown="SelectivelyIgnoreMouseButton" />
这是背后的代码：
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();
}
}
}
我认为这个方案很有效：
private void ValueText_GotFocus(object sender, RoutedEventArgs e)
{
TextBox tb = (TextBox)e.OriginalSource;
tb.Dispatcher.BeginInvoke(
new Action(delegate
{
tb.SelectAll();
}), System.Windows.Threading.DispatcherPriority.Input);
}
如果您希望将其实现为扩展方法:
public static void SelectAllText(this System.Windows.Controls.TextBox tb)
{
tb.Dispatcher.BeginInvoke(
new Action(delegate
{
tb.SelectAll();
}), System.Windows.Threading.DispatcherPriority.Input);
}
在你的GotFocus事件中：
private void ValueText_GotFocus(object sender, RoutedEventArgs e)
{
TextBox tb = (TextBox)e.OriginalSource;
tb.SelectAllText();
}
我发现上面的解决方案是因为几个月前我正在寻找一种设置给定 UIElement 焦点的方法。我在某个地方发现了下面的代码（特此致谢），它运行良好。尽管它与 OP 的问题没有直接关联，但我还是发布了它，因为它展示了使用 Dispatcher 与一个 UIElement 进行操作的相同模式。
// Sets focus to uiElement
public static void DelayedFocus(this UIElement uiElement)
{
uiElement.Dispatcher.BeginInvoke(
new Action(delegate
{
uiElement.Focusable = true;
uiElement.Focus();
Keyboard.Focus(uiElement);
}),
DispatcherPriority.Render);
}
<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();
}
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。