WPF之ViewModel中获得依赖对象控件

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ViewModel中通过附加属性的改变回调可以获得依赖对象控件

通过后代DataContext中的属性绑定到控件的附加属性上触发附加属性回调以获得控件。

数据上下文类

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public class DataContext:INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;
    private string _text;
    public string Text{
        get{return _text;}
        set{
            _text = value;
            PropertyChanged?.Invoke(this,new PropertyChangedEventArgs("Text"));
        }
    }
}

依赖属性类(可置于任何地方)

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namespace MyProperty
{
    public static class MessageInfo
    {
        //定义依赖属性
        public static readonly DependencyProperty MessageInfoProperty =
            DependencyProperty.RegisterAttached(
                "MessageInfo",
                typeof(string),
                typeof(MessageInfo),
                new PropertyMetadata(new PropertyChangedCallback(MessageInfoChanged)));
        //回调中操控依赖对象控件
        private static void MessageInfoChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var box = d as System.Windows.Controls.TextBox;
            if (null != box)
            {
                box.Text = e.NewValue as string;
                box.ScrollToEnd();
            }
        }
        //实际运行时不会进入此方法体，但编译时会以此来检查依赖属性存在与否
        public static void SetMessageInfo(System.Windows.Controls.TextBox target, string value)
        {
            //target.SetValue(MessageInfoProperty, value);
        }
    }
}

前台XAML代码

绑定的text 常规绑定

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xmlns:xc="MyProperty"

<TextBox xc:MessageInfo.MessageInfo="{Binding Text}"/>