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}" />

这篇关于MVVM和TextBox的SelectedText属性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！