MVVM和TextBox的SelectedText属性 [英] MVVM and the TextBox's SelectedText property
问题描述
我有一个带有ContextMenu的TextBox.当用户右键单击TextBox并选择适当的MenuItem时,我想在我的视图模型中获取SelectedText.我还没有找到一种以"MVVM"方式执行此操作的好方法.
I have a TextBox with a ContextMenu in it. When the user right clicks inside the TextBox and chooses the appropriate MenuItem, I would like to grab the SelectedText in my viewmodel. I have not found a good way to do this the "MVVM" way.
到目前为止,我一直在使用Josh Smith的MVVM方法.我想转移到Cinch.不知道Cinch框架是否会处理这样的问题.有想法吗?
So far I have my appliction utilizing Josh Smith's way of MVVM. I am looking to tranfer over to Cinch. Not sure if the Cinch framework will handle issues like this. Thoughts?
推荐答案
没有直接方法将SelectedText绑定到数据源,因为它不是DependencyProperty ...但是,创建附加属性非常容易,您可以而是绑定.
There's no straightforward way to bind SelectedText to a data source, because it's not a DependencyProperty... however, it quite easy to create an attached property that you could bind instead.
这是一个基本的实现:
public static class TextBoxHelper
{
public static string GetSelectedText(DependencyObject obj)
{
return (string)obj.GetValue(SelectedTextProperty);
}
public static void SetSelectedText(DependencyObject obj, string value)
{
obj.SetValue(SelectedTextProperty, value);
}
// Using a DependencyProperty as the backing store for SelectedText. This enables animation, styling, binding, etc...
public static readonly DependencyProperty SelectedTextProperty =
DependencyProperty.RegisterAttached(
"SelectedText",
typeof(string),
typeof(TextBoxHelper),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, SelectedTextChanged));
private static void SelectedTextChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
TextBox tb = obj as TextBox;
if (tb != null)
{
if (e.OldValue == null && e.NewValue != null)
{
tb.SelectionChanged += tb_SelectionChanged;
}
else if (e.OldValue != null && e.NewValue == null)
{
tb.SelectionChanged -= tb_SelectionChanged;
}
string newValue = e.NewValue as string;
if (newValue != null && newValue != tb.SelectedText)
{
tb.SelectedText = newValue as string;
}
}
}
static void tb_SelectionChanged(object sender, RoutedEventArgs e)
{
TextBox tb = sender as TextBox;
if (tb != null)
{
SetSelectedText(tb, tb.SelectedText);
}
}
}
然后您可以像在XAML中那样使用它:
You can then use it like that in XAML :
<TextBox Text="{Binding Message}" u:TextBoxHelper.SelectedText="{Binding SelectedText}" />
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