您好，我正在尝试绑定到不是 DependencyProperty 的 TextBox.CaretIndex 属性，所以我创建了一个 Behavior，但它没有按预期工作.
Hi I'm trying to bind to the TextBox.CaretIndex property which isn't a DependencyProperty, so I created a Behavior, but it doesn't work as expected.
期望(专注时)
当前行为
代码隐藏
public class TextBoxBehavior : DependencyObject
{
public static readonly DependencyProperty CursorPositionProperty =
DependencyProperty.Register(
"CursorPosition",
typeof(int),
typeof(TextBoxBehavior),
new FrameworkPropertyMetadata(
default(int),
new PropertyChangedCallback(CursorPositionChanged)));
public static void SetCursorPosition(DependencyObject dependencyObject, int i)
{
// breakpoint get never called
dependencyObject.SetValue(CursorPositionProperty, i);
}
public static int GetCursorPosition(DependencyObject dependencyObject)
{
// breakpoint get never called
return (int)dependencyObject.GetValue(CursorPositionProperty);
}
private static void CursorPositionChanged(
DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
{
// breakpoint get never called
//var textBox = dependencyObject as TextBox;
//if (textBox == null) return;
}
}
XAML
<TextBox Text="{Binding TextTemplate,UpdateSourceTrigger=PropertyChanged}"
local:TextBoxBehavior.CursorPosition="{Binding CursorPosition}"/>
更多信息
我认为这里确实有问题，因为我需要从以前从未需要的 DependencyObject 派生它，因为 CursorPositionProperty 已经是 DependencyProperty，所以这应该足够了.我还认为我需要在我的 Behavior 中使用一些事件来正确设置我的 CursorPositionProperty，但我不知道是哪个.
I think there is something really wrong here because I need to derive it from DependencyObject which was never needed before, because CursorPositionProperty is already a DependencyProperty, so this should be enough. I also think I need to use some events in my Behavior to set my CursorPositionProperty correctly, but I don't know which.
在与我的行为作斗争后，我可以为您提供 99% 可行的解决方案
After fighting with my Behavior i can present you a 99% working solution
行为
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
namespace WpfMVVMTextBoxCursorPosition
{
public class TextBoxCursorPositionBehavior : DependencyObject
{
public static void SetCursorPosition(DependencyObject dependencyObject, int i)
{
dependencyObject.SetValue(CursorPositionProperty, i);
}
public static int GetCursorPosition(DependencyObject dependencyObject)
{
return (int)dependencyObject.GetValue(CursorPositionProperty);
}
public static readonly DependencyProperty CursorPositionProperty =
DependencyProperty.Register("CursorPosition"
, typeof(int)
, typeof(TextBoxCursorPositionBehavior)
, new FrameworkPropertyMetadata(default(int))
{
BindsTwoWayByDefault = true
,DefaultUpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged
}
);
public static readonly DependencyProperty TrackCaretIndexProperty =
DependencyProperty.RegisterAttached(
"TrackCaretIndex",
typeof(bool),
typeof(TextBoxCursorPositionBehavior),
new UIPropertyMetadata(false
, OnTrackCaretIndex));
public static void SetTrackCaretIndex(DependencyObject dependencyObject, bool i)
{
dependencyObject.SetValue(TrackCaretIndexProperty, i);
}
public static bool GetTrackCaretIndex(DependencyObject dependencyObject)
{
return (bool)dependencyObject.GetValue(TrackCaretIndexProperty);
}
private static void OnTrackCaretIndex(DependencyObject dependency, DependencyPropertyChangedEventArgs e)
{
var textbox = dependency as TextBox;
if (textbox == null)
return;
bool oldValue = (bool)e.OldValue;
bool newValue = (bool)e.NewValue;
if (!oldValue && newValue) // If changed from false to true
{
textbox.SelectionChanged += OnSelectionChanged;
}
else if (oldValue && !newValue) // If changed from true to false
{
textbox.SelectionChanged -= OnSelectionChanged;
}
}
private static void OnSelectionChanged(object sender, RoutedEventArgs e)
{
var textbox = sender as TextBox;
if (textbox != null)
SetCursorPosition(textbox, textbox.CaretIndex); // dies line does nothing
}
}
}
XAML
<TextBox Height="50" VerticalAlignment="Top"
Name="TestTextBox"
Text="{Binding MyText}"
vm:TextBoxCursorPositionBehavior.TrackCaretIndex="True"
vm:TextBoxCursorPositionBehavior.CursorPosition="{Binding CursorPosition,Mode=TwoWay}"/>
<TextBlock Height="50" Text="{Binding CursorPosition}"/>
我不知道为什么它不起作用 => BindsTwoWayByDefault = true.据我所知，它对绑定没有影响，因此我需要在 XAML 中显式设置绑定模式
there is just on thing i don't know why it doesn't work => BindsTwoWayByDefault = true. it has no effect on the binding as far as i can tell you because of this i need to set the binding mode explicit in XAML
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