Is there a way to get a TextBox in Windows Phone 7 to update the Binding as the user types each letter rather than after losing focus?
Like the following WPF TextBox would do:
<TextBox Text="{Binding Path=TextProperty, UpdateSourceTrigger=PropertyChanged}"/>
Silverlight for WP7 does not support the syntax you've listed. Do the following instead:
<TextBox TextChanged="OnTextBoxTextChanged"
Text="{Binding MyText, Mode=TwoWay,
UpdateSourceTrigger=Explicit}" />
UpdateSourceTrigger = Explicitis a smart bonus here. What is it? Explicit: Updates the binding source only when you call theUpdateSourcemethod. It saves you one extra binding set when the user leaves theTextBox.
In C#:
private void OnTextBoxTextChanged( object sender, TextChangedEventArgs e )
{
TextBox textBox = sender as TextBox;
// Update the binding source
BindingExpression bindingExpr = textBox.GetBindingExpression( TextBox.TextProperty );
bindingExpr.UpdateSource();
}
I like using an attached property. Just in case you're into those little buggers.
<toolkit:DataField Label="Name">
<TextBox Text="{Binding Product.Name, Mode=TwoWay}" c:BindingUtility.UpdateSourceOnChange="True"/>
</toolkit:DataField>
And then the backing code.
public class BindingUtility
{
public static bool GetUpdateSourceOnChange(DependencyObject d)
{
return (bool)d.GetValue(UpdateSourceOnChangeProperty);
}
public static void SetUpdateSourceOnChange(DependencyObject d, bool value)
{
d.SetValue(UpdateSourceOnChangeProperty, value);
}
// Using a DependencyProperty as the backing store for …
public static readonly DependencyProperty
UpdateSourceOnChangeProperty =
DependencyProperty.RegisterAttached(
"UpdateSourceOnChange",
typeof(bool),
typeof(BindingUtility),
new PropertyMetadata(false, OnPropertyChanged));
private static void OnPropertyChanged (DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
var textBox = d as TextBox;
if (textBox == null)
return;
if ((bool)e.NewValue)
{
textBox.TextChanged += OnTextChanged;
}
else
{
textBox.TextChanged -= OnTextChanged;
}
}
static void OnTextChanged(object s, TextChangedEventArgs e)
{
var textBox = s as TextBox;
if (textBox == null)
return;
var bindingExpression = textBox.GetBindingExpression(TextBox.TextProperty);
if (bindingExpression != null)
{
bindingExpression.UpdateSource();
}
}
}
Not through binding syntax, no, but it's easy enough without. You have to handle the TextChanged event and call UpdateSource on the binding.
private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
((TextBox) sender).GetBindingExpression( TextBox.TextProperty ).UpdateSource();
}
This can be converted into an attached behavior as well pretty easily.
You can write your own TextBox Behavior to handle Update on TextChanged:
This is my sample to PasswordBox but you can simple change it to handle any property of the any object.
public class UpdateSourceOnPasswordChangedBehavior
: Behavior<PasswordBox>
{
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.PasswordChanged += OnPasswordChanged;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.PasswordChanged -= OnPasswordChanged;
}
private void OnPasswordChanged(object sender, RoutedEventArgs e)
{
AssociatedObject.GetBindingExpression(PasswordBox.PasswordProperty).UpdateSource();
}
}
Ussage:
<PasswordBox x:Name="Password" Password="{Binding Password, Mode=TwoWay}" >
<i:Interaction.Behaviors>
<common:UpdateSourceOnPasswordChangedBehavior/>
</i:Interaction.Behaviors>
</PasswordBox>
In TextChanged event call UpdateSource().
BindingExpression be = itemNameTextBox.GetBindingExpression(TextBox.TextProperty);
be.UpdateSource();
UpdateSourceTrigger=Explicit doesnt work for me, hence Im using custom class derivated from TextBox
public class TextBoxEx : TextBox
{
public TextBoxEx()
{
TextChanged += (sender, args) =>
{
var bindingExpression = GetBindingExpression(TextProperty);
if (bindingExpression != null)
{
bindingExpression.UpdateSource();
}
};
}
}
It's just one line of code!
(sender as TextBox).GetBindingExpression(TextBox.TextProperty).UpdateSource();
You can create a generic TextChanged event (for example "ImmediateTextBox_TextChanged") in the code behind of your page, and than link it to any TextBox in the page.
I took Praetorian's answer and made an extension class that inherits TextBox so you don't have to muddle up your view's code behind with this behavior.
C-Sharp:
public class TextBoxUpdate : TextBox
{
public TextBoxUpdate()
{
TextChanged += OnTextBoxTextChanged;
}
private void OnTextBoxTextChanged(object sender, TextChangedEventArgs e)
{
TextBox senderText = (TextBox)sender;
BindingExpression bindingExp = senderText.GetBindingExpression(TextBox.TextProperty);
bindingExp.UpdateSource();
}
}
VisualBasic:
Public Class TextBoxUpdate : Inherits TextBox
Private Sub OnTextBoxTextChanged(sender As Object, e As TextChangedEventArgs) Handles Me.TextChanged
Dim senderText As TextBox = DirectCast(sender, TextBox)
Dim bindingExp As BindingExpression = senderText.GetBindingExpression(TextBox.TextProperty)
bindingExp.UpdateSource()
End Sub
End Class
Then call like this in XAML:
<local:TextBoxUpdate Text="{Binding PersonName, Mode=TwoWay}"/>
