以下是用其他解决方案解决部分问题的尝试:
使用右键上下文菜单剪切/复制/过去选择所有的文本，即使你没有选择它。
当从右击上下文菜单返回时，总是选择所有文本。
当使用Alt+Tab返回应用程序时，所有文本总是被选中。
当尝试只选择第一次点击的部分文本时，总是选择全部(不像谷歌chromes地址栏)。
我写的代码是可配置的。你可以通过设置三个只读字段:SelectOnKeybourdFocus, SelectOnMouseLeftClick, SelectOnMouseRightClick来选择select all行为应该发生的动作。
这种解决方案的缺点是它更复杂，并且存储的是静态状态。它看起来像一个丑陋的斗争与TextBox控件的默认行为。尽管如此，它仍然可以工作，并且所有代码都隐藏在Attached Property容器类中。
public static class TextBoxExtensions
{
// Configuration fields to choose on what actions the select all behavior should occur.
static readonly bool SelectOnKeybourdFocus = true;
static readonly bool SelectOnMouseLeftClick = true;
static readonly bool SelectOnMouseRightClick = true;
// Remembers a right click context menu that is opened
static ContextMenu ContextMenu = null;
// Remembers if the first action on the TextBox is mouse down
static bool FirstActionIsMouseDown = false;
public static readonly DependencyProperty SelectOnFocusProperty =
DependencyProperty.RegisterAttached("SelectOnFocus", typeof(bool), typeof(TextBoxExtensions), new PropertyMetadata(false, new PropertyChangedCallback(OnSelectOnFocusChanged)));
[AttachedPropertyBrowsableForChildren(IncludeDescendants = false)]
[AttachedPropertyBrowsableForType(typeof(TextBox))]
public static bool GetSelectOnFocus(DependencyObject obj)
{
return (bool)obj.GetValue(SelectOnFocusProperty);
}
public static void SetSelectOnFocus(DependencyObject obj, bool value)
{
obj.SetValue(SelectOnFocusProperty, value);
}
private static void OnSelectOnFocusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (!(d is TextBox textBox)) return;
if (GetSelectOnFocus(textBox))
{
// Register events
textBox.PreviewMouseDown += TextBox_PreviewMouseDown;
textBox.PreviewMouseUp += TextBox_PreviewMouseUp;
textBox.GotKeyboardFocus += TextBox_GotKeyboardFocus;
textBox.LostKeyboardFocus += TextBox_LostKeyboardFocus;
}
else
{
// Unregister events
textBox.PreviewMouseDown -= TextBox_PreviewMouseDown;
textBox.PreviewMouseUp -= TextBox_PreviewMouseUp;
textBox.GotKeyboardFocus -= TextBox_GotKeyboardFocus;
textBox.LostKeyboardFocus -= TextBox_LostKeyboardFocus;
}
}
private static void TextBox_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
if (!(sender is TextBox textBox)) return;
// If mouse clicked and focus was not in text box, remember this is the first click.
// This will enable to prevent select all when the text box gets the keyboard focus
// right after the mouse down event.
if (!textBox.IsKeyboardFocusWithin)
{
FirstActionIsMouseDown = true;
}
}
private static void TextBox_PreviewMouseUp(object sender, MouseButtonEventArgs e)
{
if (!(sender is TextBox textBox)) return;
// Select all only if:
// 1) SelectOnMouseLeftClick/SelectOnMouseRightClick is true and left/right button was clicked
// 3) This is the first click
// 4) No text is selected
if (((SelectOnMouseLeftClick && e.ChangedButton == MouseButton.Left) ||
(SelectOnMouseRightClick && e.ChangedButton == MouseButton.Right)) &&
FirstActionIsMouseDown &&
string.IsNullOrEmpty(textBox.SelectedText))
{
textBox.SelectAll();
}
// It is not the first click
FirstActionIsMouseDown = false;
}
private static void TextBox_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
if (!(sender is TextBox textBox)) return;
// Select all only if:
// 1) SelectOnKeybourdFocus is true
// 2) Focus was not previously out of the application (e.OldFocus != null)
// 3) The mouse was pressed down for the first after on the text box
// 4) Focus was not previously in the context menu
if (SelectOnKeybourdFocus &&
e.OldFocus != null &&
!FirstActionIsMouseDown &&
!IsObjectInObjectTree(e.OldFocus as DependencyObject, ContextMenu))
{
textBox.SelectAll();
}
// Forget ContextMenu
ContextMenu = null;
}
private static void TextBox_LostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
if (!(sender is TextBox textBox)) return;
// Remember ContextMenu (if opened)
ContextMenu = e.NewFocus as ContextMenu;
// Forget selection when focus is lost if:
// 1) Focus is still in the application
// 2) The context menu was not opened
if (e.NewFocus != null
&& ContextMenu == null)
{
textBox.SelectionLength = 0;
}
}
// Helper function to look if a DependencyObject is contained in the visual tree of another object
private static bool IsObjectInObjectTree(DependencyObject searchInObject, DependencyObject compireToObject)
{
while (searchInObject != null && searchInObject != compireToObject)
{
searchInObject = VisualTreeHelper.GetParent(searchInObject);
}
return searchInObject != null;
}
}
要将附加属性附加到一个文本框，你所需要做的就是添加附加属性的xml名称空间(xmlns)，然后像这样使用它:
<TextBox attachedprop:TextBoxExtensions.SelectOnFocus="True"/>
关于这个解决方案的一些注意事项:
若要覆盖鼠标按下事件的默认行为，并启用在第一次单击时只选择部分文本，则在鼠标按下事件时选择所有文本。
我不得不处理的事实，文本框记得它的选择后失去焦点。实际上我已经重写了这个行为。
我必须记住，如果鼠标按下是TextBox (FirstActionIsMouseDown静态字段)上的第一个动作。
我必须记住右键打开的上下文菜单(ContextMenu静态字段)。
我发现唯一的副作用是当SelectOnMouseRightClick为真。有时右键单击上下文菜单闪烁时，它打开和右键单击空白的文本框不做“全选”。
