"UpdateSourceTrigger = PropertyChanged"等效于Windows Phone 7 TextBox

Question

有没有办法让Windows Phone 7中的TextBox更新Binding,因为用户键入每个字母而不是失去焦点？

像下面的WPF TextBox一样:

<TextBox Text="{Binding Path=TextProperty, UpdateSourceTrigger=PropertyChanged}"/>

Answer 1

WP7的Silverlight不支持您列出的语法.请执行以下操作:

<TextBox TextChanged="OnTextBoxTextChanged"
         Text="{Binding MyText, Mode=TwoWay,
                UpdateSourceTrigger=Explicit}" />

UpdateSourceTrigger = Explicit这里是一个聪明的奖金.它是什么？ 显式:仅在调用UpdateSource方法时更新绑定源.当用户离开时,它会为您节省一个额外的绑定集TextBox.

在C#中:

private void OnTextBoxTextChanged( object sender, TextChangedEventArgs e )
{
  TextBox textBox = sender as TextBox;
  // Update the binding source
  BindingExpression bindingExpr = textBox.GetBindingExpression( TextBox.TextProperty );
  bindingExpr.UpdateSource();
}

Answer 2

我喜欢使用附属物.以防万一你进入那些小虫子.

<toolkit:DataField Label="Name">
  <TextBox Text="{Binding Product.Name, Mode=TwoWay}" c:BindingUtility.UpdateSourceOnChange="True"/>
</toolkit:DataField>

然后是支持代码.

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();
  }
}
}

Answer 3

不是通过绑定语法,不是,但没有它很容易.您必须处理TextChanged事件并在绑定上调用UpdateSource.

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
    ((TextBox) sender).GetBindingExpression( TextBox.TextProperty ).UpdateSource();
}

这可以非常容易地转换为附加行为.