silverlight - two - wpf binding textbox

¿Cómo vincular SelectionStart Property of Text Box?

Question

Yo uso esto:

<TextBox x:Name="Test"/>
<TextBlock Text="{Binding SelectionStart, ElementName=Test}"/>

pero siempre muestra 0.
¿Cómo puedo tratarlo?
Gracias.

Answer 1

No puede vincularse a SelectionStart porque no es DependencyProperty.

Answer 2

Hasta donde yo sé, esta característica no se ha incluido en Silverlight 2.0.

Lea este artículo para una solución alternativa.

Answer 3

Me encontré con este problema (SelectionStart y SelectionLength no son propiedades de dependencia) y decidí hacer un TextBox con inicio y fin de selección enlazables:

public class SelectionBindingTextBox : TextBox
{
public static readonly DependencyProperty BindableSelectionStartProperty =
DependencyProperty.Register(
"BindableSelectionStart",
typeof(int),
typeof(SelectionBindingTextBox),
new PropertyMetadata(OnBindableSelectionStartChanged));
public static readonly DependencyProperty BindableSelectionLengthProperty =
DependencyProperty.Register(
"BindableSelectionLength",
typeof(int),
typeof(SelectionBindingTextBox),
new PropertyMetadata(OnBindableSelectionLengthChanged));
private bool changeFromUI;
public SelectionBindingTextBox() : base()
{
this.SelectionChanged += this.OnSelectionChanged;
}
public int BindableSelectionStart
{
get
{
return (int)this.GetValue(BindableSelectionStartProperty);
}
set
{
this.SetValue(BindableSelectionStartProperty, value);
}
}
public int BindableSelectionLength
{
get
{
return (int)this.GetValue(BindableSelectionLengthProperty);
}
set
{
this.SetValue(BindableSelectionLengthProperty, value);
}
}
private static void OnBindableSelectionStartChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
{
var textBox = dependencyObject as SelectionBindingTextBox;
if (!textBox.changeFromUI)
{
int newValue = (int)args.NewValue;
textBox.SelectionStart = newValue;
}
else
{
textBox.changeFromUI = false;
}
}
private static void OnBindableSelectionLengthChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
{
var textBox = dependencyObject as SelectionBindingTextBox;
if (!textBox.changeFromUI)
{
int newValue = (int)args.NewValue;
textBox.SelectionLength = newValue;
}
else
{
textBox.changeFromUI = false;
}
}
private void OnSelectionChanged(object sender, RoutedEventArgs e)
{
if (this.BindableSelectionStart != this.SelectionStart)
{
this.changeFromUI = true;
this.BindableSelectionStart = this.SelectionStart;
}
if (this.BindableSelectionLength != this.SelectionLength)
{
this.changeFromUI = true;
this.BindableSelectionLength = this.SelectionLength;
}
}
}

Answer 4

Esta podría ser una solución alternativa:

Ver:

<TextBox Text="{Binding Text}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<mvvml:EventToCommand Command="{Binding TextBoxSelectionChangedCommand}"
PassEventArgsToCommand="True" />
</i:EventTrigger>
</i:Interaction.Triggers>
</TextBox>

ViewModel:

 #region TextBoxSelectionChangedCommand
RelayCommand<RoutedEventArgs> _TextBoxSelectionChangedCommand = null;
public ICommand TextBoxSelectionChangedCommand {
get {
if (_TextBoxSelectionChangedCommand == null) {
_TextBoxSelectionChangedCommand = new RelayCommand<RoutedEventArgs>((r) => TextBoxSelectionChanged(r), (r) => true);
}
return _TextBoxSelectionChangedCommand;
}
}
protected virtual void TextBoxSelectionChanged(RoutedEventArgs _args) {
YourCursorPositionVariable = (_args.OriginalSource as System.Windows.Controls.TextBox).SelectionStart;
}
#endregion

Estoy de acuerdo en que tiene que copiar el tipo de componente TextBox en ViewModel y es un tipo de acoplamiento, pero crear un componente personalizado impondrá también vincular una propiedad específica.